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648 Background: The oral tyrosine kinase inhibitor Cabozantinib (CABO) is frequently used to treat patients with metastatic RCC. Polypharmacy is common in elderly pts, thus several drug-drug interactions (DDIs) with cabozantinib may ensue. Methods: ZEBRA /MEET-URO 9 was a prospective, real world trial enrolling pts ≥ 70 years with mRRC treated with CABO at 13 Italian Oncology Centers. All concomitants drugs administered to pts were collected and categorized according to active principles and indication. DDIs were identified through a dedicated software (Lexicomp), scientific databases (Sider4.1) and published articles. Results: we enrolled 104 pts, median age 75.8 years (range 70.2-87.4 yrs). Overall, 91.4% of the cohort was treated at a reduced dose either upfront or due to side effects. Pts took a median of 6 concomitant drugs (IQR: 4-9), for a total of 131 active principles. Software analysis identified 4 DDIs (warfarin, apixaban, diltiazem and furosemide); whereas scientific reports allowed us to identify 15 additional DDIs involving metoprolol, nebivolol, olmesartan, amiloride, simvastatin, rosuvastatin, polyenoic omega-3 fatty acids, loperamide, metoclopramide, metformin, dutasteride, dexamethasone, prednisone, cetirizine and doxazosin. Seventy pts with potential DDIs experienced a trend for higher rate of grade 3-4 adverse events compared to other pts, although difference was not statistically significant (48.7% v 23.5 %, p=0.485). The table summarizes the main DDIs and suggestions to avoid or mitigate their effects Conclusions: the risk of DDIs was not negligible in our cohort of elderly mRCC pts treated with CABO, although the frequent dose reductions of CABO probably confounded their impact on toxicities. Unremitting attention to concomitant medications in the elderly is thus warranted. [Table: see text]

637 Background: The combination of neutrophil to lymphocyte (NLR), bone metastases and IMDC score in the novel prognostic Meet-URO score has shown a higher prognostic performance than the IMDC score alone in mRCC pts receiving ≥2nd line nivolumab or cabozantinib in two retrospective analyses and 1st line nivolumab-ipilimumab in a real-world prospective study [http://bit.ly/Meet-URO15_score]. Further validation is needed since this score represents an easy prognostic tool for clinical practice with no additional costs. Methods: A real-world analysis of elderly (≥70 yo) mRCC pts treated with any line cabozantinib was conducted in the multicenter observational prospective Zebra study. Baseline Meet-URO score was assessed. The primary endpoint was overall survival (OS) and the Harrell’s c-index was calculated to compare accuracy of survival prediction of the Meet-URO and IMDC scores. Results: 104 mRCC pts received cabozantinib as 1st (38%), 2nd (20%), 3rd (33%) and 4th (8%) line, with a median follow-up of 11.2 months (mo) and a median overall survival (mOS) of 18.4 mo. According to the IMDC score, favorable- (15%), intermediate- (65%) and poor-risk (19%) pts had a mOS not reached (NR), 15.6 and of 5.7 mo, respectively (p = 0.011). Reclassifying the population according to the Meet-URO score, we observed that group 1 (10%) and group 2 (25%) had both mOS NR, whereas group 3 (33%), group 4 (25%) and group 5 (8%) had a mOS of 13.6, 12.5 and 3.7 mo, respectively (p = 0.001). Moreover, the Meet-URO score maintained its discrimination ability also merging group 1-2 vs 3-4 vs 5 (p < 0.001). NLR < 3.2 was the heaviest component of the score (p < 0.001, mOS 24.8 vs 11.5 mo). The Meet-URO score (using both original with 5 groups and modified with 3 groups) has shown a higher prognostic power than the IMDC score alone (c-index of 0.686 and 0.676 vs 0.622). Conclusions: This analysis confirmed the higher accuracy in survival stratification of the Meet-URO score compared with the IMDC score alone also in a specific population like elderly mRCC pts treated with cabozantinib. NLR was confirmed as a strong prognostic factor with cabozantinib. Further applications of the Meet-URO score in mRCC pts treated with first-line immune-combinations are planned and highly awaited. Clinical trial information: 2018/116/PU .

469 Background: In the phase 3 JAVELIN Bladder 100 trial (NCT02603432), avelumab (anti–PD-L1) 1LM plus best supportive care (BSC) in patients (pts) with la/mUC whose disease did not progress after 1L platinum-based chemotherapy (PBC) significantly extended overall survival (OS) vs BSC alone, and it is now recommended internationally as standard of care with level 1 evidence. We report real-world descriptive pt characteristics and outcomes data from a large, multicenter, Italian compassionate use program (CUP) assessing avelumab 1LM in pts with la/mUC. Methods: This prospective, noninterventional CUP was initiated on Jan 18, 2021, to provide early access to avelumab before reimbursement by the Italian Medicines Agency for pts with la/mUC. Avelumab was provided upon physician request and after approval by local ethics committees in accordance with the Italian compassionate use regulation. Avelumab 800 mg IV was administered every 2 weeks per local prescribing information to adult pts aged ≥18 years with la/mUC who were progression-free following PBC (4-6 cycles, starting 4-10 weeks after last dose of PBC). Pts who had a relapse within 12 months of prior adjuvant or neoadjuvant systemic therapy, including immune checkpoint inhibitors, were not eligible. Results: As of Aug 16, 2022, 464 pts (78.4% male, 21.6% female) were included from 140 Italian centers from Jan 2021-Mar 2022. Median age at inclusion was 70 years (IQR, 63-76 years). At the start of 1L PBC, 346 pts (73.9%) had metastatic disease and 40 (8.6%) had unresectable locally advanced disease (disease stage not defined [N/D] in 78 pts [16.8%]). ECOG PS was 0 in 321 pts (69.2%), 1 in 140 (30.2%), and N/D in 3 (0.7%). Primary tumor site was upper tract in 148 pts (31.9%) and lower tract in 309 (66.6%) (N/D in 7 [1.5%]). 1L PBC comprised carboplatin + gemcitabine in 241 pts (51.9%), cisplatin + gemcitabine in 214 (46.1%), and other PBC in 9 (1.9%); 225 pts (48.5%) received 4 cycles of PBC, 54 (11.6%) received 5 cycles, and 177 (38.2%) received 6 cycles (other or N/D in 8 [1.7%]). Complete response to 1L PBC was achieved in 51 pts (11.0%), partial response in 266 (57.3%), and stable disease in 147 (31.7%). For 391 pts currently evaluable for OS and progression-free survival (PFS) from the start of avelumab, the 12-month OS rate was 69.1% (95% CI, 64.4%-73.6%), while median OS was not reached. The 12-month PFS rate was 38.9% (95% CI, 34.0%-43.7%) and median PFS was 6.6 months (95% CI, 5.6-8.9 months). Grade 3-4 adverse events occurred in 33 pts (7.1%). Conclusions: This CUP included a large pt population representative of daily clinical practice in 140 Italian oncology centers and the results are consistent with those of previous studies. Overall, these real-world data strengthen the findings of JAVELIN Bladder 100 and provide further support for avelumab 1LM as a standard of care in eligible pts with la/mUC.

647 Background: Cabozantinib (CABO) is an oral tyrosine kinase inhibitor registered for the treatment of metastatic renal cell carcinoma (mRCC) for the first or subsequent lines. Tolerability in real world elderly patients is poorly documented. G8 is a short test for vulnerability gaining increased interest as a screening tool for trials in geriatric oncology. Methods: ZEBRA/MEET-URO 9 was a prospective multicenter study of safety and activity of CABO administered to pts ≥70 years with mRCC, either in the first or subsequent lines of treatment, until progression or unacceptable toxicity. All pts underwent G8 score at baseline, with a cut-off for vulnerability of 14 or below. Data on tolerability and activity were collected prospectively after signature of informed consent. Results: A total of 104 pts started CABO at 13 Italian Centers, 38,5% as first line. Median age was 75.8 yrs (range 70.2-87.4 yrs, 26 pts ≥80 yrs), 73.1% males. IMDC score was good 19.2%, intermediate 53.9%, poor 26.9%. Primary tumor had been removed in 82.7% of pts, histology was clear cell 78.8%, papillary 8.7%, chromophobe 5.8%, unclassified 6.7%. G8 score was ≤14 in 65.4% of pts. Up-front dose reduction of CABO was more frequent in pts with low G8 score (79.4 vs 41.7%, p=0.003), but eventually the majority of pts (91.4%) underwent dose reductions of CABO. After a median treatment of 6.4 months (0.5-26.1 months), 38.4% of pts developed G3-4 toxicities, 22.1% interrupted treatment due to adverse events, 2.8% (3 pts) died due to cardiovascular or thromboembolic events. Median PFS was 7.6 months (95% CI=5.8-12.6 months) in first line, 10.0 months (5.8-15.6) in second or further lines, median OS was 20.1 months (11.1-not reached) and 15.6 months (12.5-not reached), respectively. G8 score ≤14 did not correlate with rate of temporary interruptions >7 days, hospitalization, incidence of G3-5 toxicities, as well as with PFS. Pts with G8 score ≤14 had a trend for reduced OS, but difference was not statistically significant both in the first and further lines of treatment. Conclusions: Screening G8 test was positive in more than a half of pts, underlying the need for detailed geriatric assessment and increased clinical monitoring of such patients. A G8 score ≤14 correlated with up-front dose reduction of CABO but not with G3-5 toxicities probably due to the high rates of dose reductions in the whole cohort. Correlation between low G8 score and OS could not be demonstrated in this population.

214 Background: Up to 80% of mCRPC have bone metastases and about 25% of metastatic prostate cancer harbor mutations in DNA damage repair defects (DDR). DDR gene mutations are a negative prognostic factor, being associated with short metastasis-free survival and cancer-specific survival. We analyzed the impact of somatic mutations in DDR genes on bone-related efficacy endpoints in mCRPC. Methods: We retrospectively analyzed the mutational status of mCRPC patients per FoundationOne analysis in tissue biopsy or, when it was not possible, in liquid biopsy (performed at the onset of mCRPC). We evaluated the impact of DDR gene mutations on bone-related efficacy endpoints at the time of mCRPC diagnoses, by dividing patients in two main groups (mutated DDR, specifically, mutations in at least one of BRCA1/2, ATM, FANCA, ATR, CHEK2, RAD51, PALB2, and CDK12 genes: group A; wild-type DDR: group B). We investigated differences between the two groups in terms of time from bone metastases onset to death, skeletal metastatic tumor burden (sites and number of lesions), skeletal-related events (SRE) incidence, and time to first on-study SRE. Results: Of the 131 patients with mCRPC enrolled, 115 had bone metastases. Clinical data distribution, according to molecular profile, is presented. There is no difference in terms of sites of metastases and time from bone metastases onset to death between the 2 groups. Mutated DDR status was associated with bone metastases volume (p = 0.0325), but did not affect SRE incidence and time to SRE onset. Conclusions: In our analysis, mutated DDR status was associated with higher bone metastases volume, although a not detrimental effect on the other bone-related efficacy endpoints was observed. [Table: see text]

107 Background: The optimal management of mCRPC in men aged ≥75 is challenging, and there is a paucity of clinical data in the literature. Although AA and E are commonly used as 1st line Rx for mCRPC, it is unclear whether use of upfront D for mCSPC may impact their clinical efficacy or safety in this elderly population. Methods: Patients aged ≥75 who started AA or E as 1st line Rx for mCRPC within January 2015 - April 2019 were identified from the IRB approved databases of 10 institutions in Europe, South and North America. Demographic and clinicopathological data were collected from available medical records, including Gleason, prior local therapy, newly diagnosed metastatic disease, disease volume, ECOG, PSA and sites of metastases. Patients were classified by use of upfront D for mCSPC. The primary endpoints were overall survival (OS) from AA/E onset and OS from ADT start and safety of AA/E. The endpoints distributions including median (95% CI) were estimated by Kaplan-Meier method. Results: Of the 337 patients selected, 24 (7.1%) received ADT+D and 313 (92.9%) ADT alone for mCSPC. Patients with ADT+D tended to be younger (78 vs 81, p=0.022) and, albeit not statistically significant, had higher rates of Gleason score >8 (81.0% vs 62.6%, p=0.10), newly diagnosed (83.3% vs 65.6%, p=0.08) and high volume disease (45.8% vs 34.6%, p=0.28), compared to those with ADT alone. Median follow-up was 18.8 months. No significant difference of OS from ADT start or from AA/E onset was observed between the 2 cohorts (see table). Despite OS from ADT start being longer in those having ADT+D, OS from AA/E start was approximately 2 years in both cohorts. Rates of adverse events (AEs) of any grade (58.3% vs 52.1%, p=0.67) and grade ≥3 (12.5% vs 15.7%, p=1.0) did not significantly differ between the 2 cohorts. Conclusions: While limited by small sample size for ADT+D and retrospective study design, patients aged ≥75 having AA/E as 1st line mCRPC Rx showed similar survival outcomes and tolerability regardless of previous use of D for mCSPC. [Table: see text]

166 Background: About 2/3 of all prostate cancer (PCa) deaths occur in patients aged ≥75, who are frequently diagnosed with advanced PCa. ARSi abiraterone acetate (AA) and enzalutamide (E) are the most common 1st line Rx for patients with mCRPC. Yet, the optimal treatment sequence for the elderly ≥75 after ARSi failure is still unclear. Methods: Using available medical records, patients aged ≥75 who started ARSi as 1st line Rx for mCRPC within January 2015 - April 2019 and, upon progression, 2nd line alternative ARSi or D were identified from the IRB approved hospital registries of 10 centers in Europe, North and South America. Patients were categorized by type of 2nd line Rx for mCRPC into cohorts AA/E and D. Primary endpoints were overall survival (OS) from 1st line AA/E start, OS and radiographic progression-free survival (rPFS) from 2nd line Rx start, and safety. The Kaplan Meier method was used to calculate endpoint distributions and medians (95% CI). Results: Of the 122 patients identified, 57 (46.7%) had AA/E and 65 (53.3%) D, as 2nd line Rx for mCRPC. Median follow-up was 26.3 months (95% CI, 23.1-27.9 months). Cohort AA/E tended to be older (81 vs 78 years; p=0.001) and with high-volume disease (45.5% vs 25.0%; p=0.022) compared to cohort D. No significant difference in OS from 1st line ARSi onset and OS or rPFS from 2nd line Rx start was found between the 2 cohorts. Cohort AA/E had longer rPFS than cohort D, albeit not significant (18.5 vs 12.0 months; p=0.13). Rates of adverse events (AEs) of any grade (42.1 vs 53.8; p=0.21) and AEs of grade ≥3 (19.3% vs 18.5%; p=1.0) did not show significant differences between the 2 cohorts. Conclusions: Within the limitations of small cohorts and retrospective design, treatment sequences with 2nd line AA/E or D after failure of 1st line alternative ARSi for mCRPC showed similar efficacy and safety in the elderly ≥75 years old.

129 Background: Rechallenge therapy with epidermal growth factor receptor (EGFR) inhibitors in chemo-refractory metastatic colorectal cancer (mCRC) is an emerging therapeutic approach. Trifluridine-tipiracil is approved for treatment of chemo-refractory mCRC patients. Methods: Chemo-refractory RAS WT mCRC patients, that had a major response (partial or complete response) to first-line chemotherapy plus an anti-EGFR monoclonal antibody and had an-anti-EGFR drug-free interval during second-line therapy of four or more months were randomized in a phase II trial to assess the addition of the anti-EGFR monoclonal antibody panitumumab to trifluridine-tipiracil as third-line rechallenge therapy. The primary endpoint was progression free survival (PFS). Baseline plasma was analyzed for circulating free tumor (ct) DNA by using Biocartis Idylla platform to detect mutations in KRAS, NRAS, BRAF ( V600E) and EGFRextracellular domain ( S492R). In 24 patients with baseline RAS/BRAF wild type (WT) ctDNA, Foundation One liquid CDx (324 gene profiling) was also performed before treatment and at disease progression. Results: 62 patients were treated with trifluridine-tipiracil (31 patients, arm A) or with trifluridine-tipiracil plus panitumumab (31 patients, arm B). As of September 16, 2022, 1 patient in arm A and 2 patients in arm B were on treatment. The primary endpoint was met. Median PFS (mPFS) was 4 months in arm B versus 2.5 months in arm A [hazard ratio (HR): 0.48; 95% CI 0.28-0.82; P = 0.007]. Baseline plasma RAS/BRAF WT ctDNA was found in 23/31 patients in Arm A and in 26/31 patients in Arm B. In this group, mPFS was 4.5 months in Arm B versus 2.6 months in Arm A (HR: 0.48; 95% CI 0.26-0.89; P = 0.019). Disease control (major responses plus stable disease) was higher for patients in Arm B compared to Arm A (81% versus 48%), whereas disease progression was the best response in 19% versus 52% patients, respectively. PFS rates at 6 and 12 months were 38.5% and 15.4% in arm B versus 13% and 0% in arm A. At disease progression, Foundation One liquid CDx detected several mutations within the EGFR pathway, which could correlate with cancer cell resistance to panitumumab. Conclusions: This is the first prospective randomized trial which evaluated anti-EGFR monoclonal antibody (panitumumab) in addition to standard of care (trifluridine-tipiracil) as third-line rechallenge therapy in chemo-refractory RASWT mCRC patients. Baseline liquid biopsy allows selection of RAS/BRAF WT ctDNA patients who could have a relevant clinical benefit. Clinical trial information: NCT05468892 .

3503 Background: Continuous anti-EGFR-based FOLFIRI is a first-line standard of care in pts with RAS/BRAF wt mCRC. The emergence of resistance and treatment-related toxicity limit the efficacy of continuous treatment. Thus, an intermittent strategy could reduce both toxicity and resistance. Methods: This is a prospective, randomized, non-comparative, open-label, multicenter phase II study. Unresectable, previously untreated RAS/BRAF wt mCRC pts, were randomized to a control arm (A) receiving FOLFIRI/PANI continuously until progression or to the experimental arm (B), receiving 8 cycles of the same regimen followed by a treatment free interval. This lasted untill progressive disease, when another treatment period of up to 8 cycles was restarted. This intermittent strategy was continued until progression occurred on treatment. Tumor assessment was always done every 8 weeks in both arms. Pts were stratified for center, ECOG PS (0-1 vs 2), previous adjuvant therapy (yes or no), sidedness (right vs left) and metastatic sites (1 vs ≥ 2). The primary endpoint was the progression-free survival on treatment (PFSOT) at 1 year. Assuming p1=43% PFSOT at 1 year, corresponding to an expected median PFSOT time ≥ 10 months in the experimental arm, and a 5% drop-out rate, a sample size of 68 pts in each arm granted the study a power of 80%, with a type I error of 10% (binomial test) for rejecting the null hypothesis, p0=30%, corresponding to a median PFSOT time of ≤ 7 months. Secondary endpoints were safety, quality of life, OS and response rate (ORR); ctDNA samples were also collected. No formal comparison between the two arms was planned. Results: From May 2018 to June 2021, 137 pts were randomized (69 arm A/68 arm B). Main pts’ characteristics were (arm A/B): males 59/61%; median age 62/66yrs; PS 0 84/72%; right colon 17/15%; previous adjuvant therapy 22/29%; single metastatic site 33/26%. At a median follow-up of 18 months (IQR: 10-26), median PFS OT was 12.6 months (95% CI: 9.0-16.1) in arm A and 17.6 months (95% CI: 7.5-27.8) in arm B with a 1 year PFSOT rate of 51.7% and 61.3%, respectively. ORR (arm A/B) was 64/56%. Median number of FOLFIRI/PANI cycles administered per patient were (arm A/B) 13/12. Main grade 3-4 toxicities were (arm A/B): skin 27/13%, neutropenia 23/22%; diarrhea 13/15%. Conclusions: The primary endpoint of the study was met with the intermittent FOLFIRI-PANI strategy producing a long PFS with a reduced skin toxicity. These data deserve further investigations in a phase III trial. Clinical trial information: NCT04425239.

439 Background: Avelumab (ave) was approved as maintenance therapy after platinum-based first line (1L) therapy for patients (pts) with aUC based on ph. 3 Javelin Bladder 100 study (NCT02603432), showing significant overall survival (OS) improvement. Here we tested the activity of ave as 1L of therapy in cis-unfit pts with aUC and PD-L1+ve expression. Methods: ARIES is a single-arm, multi-site, open-label phase II trial. Enrolled pts had aUC, were cis-unfit (at least one of: ECOG-PS = 2, CrCl < 60 mL/min, grade ≥2 peripheral neuropathy/hearing loss, progression within 6-mos before the end of neo/adj chemo), had not previously received chemo for aUC and PD-L1≥5% (SP263) centrally assessed. Pts received ave 10 mg/Kg IV Q2W until progression, unacceptable toxicity and withdrawal, whichever occurred first. The primary endpoint was the 1-year OS. Key secondary endpoints were median-OS, -PFS, ORR and safety. Results: A total of 198 eligible cis-unfit pts have been tested for PD-L1 and 71 (35.6%) have been found positive. Among enrolled patients (N = 71), median age was 75 y, 35 (49.3%) had visceral disease, and 22 (31.0%) had ECOG-PS = 2; 50 (70.4%) had CrCl < 60 mL/min and 9 (12.7%) progressed within 6-mos from the end of neo/adj chemo. At the cut-off data (Oct 7, 2021), median follow up was 9.0 mo and 13 patients are still on treatment. The median OS was 10.0 mos (95% CI, 5.7-14.3), and 40.8% of patients were alive at 1-year. The ORR for all patients was 22.5%; complete response, 1.4% (n = 1); partial response, 21.1% (n = 15). Clinical benefit was 43.6% (n = 31). Median PFS was 2.0 mos (95% CI, 1.4-2.6). Among the 56 pts who received at least 3 cycles (29 days) of therapy the median OS was 16.0 vs 1.0 mos. Five (7.0%) grade 3 ave-related adverse events, and no treatment-related death were reported. Conclusions: Ave is active and safe in pts with cis-unfit, PD-L1+ve aUC and poor baseline characteristics. Clinical trial information: NCT03891238.

3578 Background: Promising antitumor activity of so called rechallenge treatment with anti-epidermal growth factor receptor (EGFR) drugs in patients with RAS wild type (RAS WT) metastatic colorectal cancer (mCRC) has been recently reported. Beside the absence of resistance mutations at plasma circulating tumor DNA (ctDNA) analysis, no biomarkers of response to anti-EGFR rechallenge strategy have been identified. Methods: We conducted the single arm phase II CAVE mCRC trial to evaluate the combination of cetuximab as rechallenge plus avelumab treatment in 77 RAS WT mCRC patients, with complete (CR) or partial response (PR) to first line chemotherapy plus anti-EGFR drugs, who developed acquired resistance and received a subsequent line of therapy. A post-hoc baseline analysis of circulating tumor DNA (ctDNA) for KRAS, NRAS, BRAF and EGFR-S492R mutations was performed for 67/77 (87%) patients. The correlation of skin toxicity (ST) and other clinical variables with OS, PFS and response rate (RR) was assessed. Results: Cetuximab plus avelumab provided in the intention to treat population (ITT) median overall survival (mOS) of 11.6 months [95% Confidence Interval (CI), 8.4-14.8] and median PFS (mPFS) of 3.6 months (95% CI, 3.2-4.1) with a manageable toxicity profile. Thirty-three (42.9%) patients experienced grade 2-3 ST with mOS of 17.8 months (CI 95% 14.9-20.7), whereas 44 (57.1%) patients with grade 0-1 ST exhibited mOS of 8.2 months (CI 95% 5.6-11), (HR 0.51, CI 95% 0.29-0.89, P = 0.019). mPFS was 4.6 months (CI 95% 3.5-5.8) in patients with grade 2-3 ST, compared to 3.4 months (CI 95% 2.8-4.1) in patients with grade 0-1 ST (HR 0.49, CI 95% 0.3-0.8, P = 0.004). Grade 2-3 ST and baseline RAS/BRAF/EGFR WT ctDNA were the only variables with statistically significant effect on OS both at univariate and multivariate analyses. ST, number of metastatic sites ≤2, surgery of primary tumor and RAS/BRAF/EGFR WT ctDNA were associated with an improvement in PFS only at univariate analysis. In the 33 patients with grade 2-3 ST, 1 (3%) CR, 2 (6.1%) PR and 24 (72.7%) stable disease (SD) were observed, with disease control rate (DCR) of 81.8%. In the 44 patients with grade 0-1 ST 0 CR, 3 (6.8%) PR, 20 (45.5%) SD, with 52.3% DCR were reported. Conclusions: Cetuximab plus avelumab is effective and well tolerated as rechallenge treatment in mCRC. ST is a clinical biomarker for the identification of RAS/BRAF mCRC patients that could benefit from anti-EGFR rechallenge. Clinical trial information: NCT04561336.

5052 Background: Enzalutamide is a second-generation androgen receptor inhibitor that showed to prolong survival in different setting of prostate cancer. Visceral metastases, occurring in 10–30% of mCRPC pts, have been associated with poor outcomes. Given the poor prognosis, trial investigating hormone therapies often excluded men with visceral disease, especially in the pre-docetaxel setting. To date, there are no prospective studies designed ad hoc to test hormone therapies in this subgroup of pts. Methods: In this open label phase II multicentre study mCRPC pts with visceral metastases were treated with enzalutamide 160 mg orally once daily as first or second line after docetaxel until progressive disease or unacceptable toxicity. Pts were eligible if they had documented measurable metastatic visceral disease (according to RECIST 1.1 criteria), including lesions in lung or liver or extraregional lymphnodes. Pts must have PSA progression or radiographic progression (according to PCWG2). Primary endpoint was to determine the clinical benefit, as measured by 3-months (mo) disease control rate (DCR) defined as the proportion of pts with best overall response of confirmed complete (CR) or partial responses (PR) or stable disease as per RECIST 1.1 at mo 3. Secondary endpoints were safety, quality of life (assessed by EQ-5D-5L e FACT-P questionnaire), pain assessment (by BPI-SF questionnaire). Exploratory objectives were to assess the association between ARv7 splicing variants (in CTCs samples) and treatment response/resistance. For CTC and ARv7 detection, we used the Adna test Prostate Cancer Panel. Results: From March 2017 through January 2021, 68 pts were enrolled at 6 Italian centres. One pt never started treatment because of withdrawal of consent. Median age was 70 years (IQR 65- 78). All pts presented with visceral disease at baseline: 27, 6, 55 pts presented with lung, liver and lymphnodes lesions, respectively. 26 pts presented with only one metastatic site, 22 pts with two, while the remaining part with multiple sites. 15 pts received a previous treatment with docetaxel in the mCRPC phase. The median follow-up was 10 mo. The median time on treatment was 8 mo. At mo 3, 24 pts presented a stable disease, 1 pt achieved a confirmed CR and 20 pts a PR for a 3 mo-DCR of 67% (45/67). Discontinuations due to adverse-events, disease-related death, or disease progression occurred in 6%, 7%, and 40% of pts, respectively. So far, only 26 patients were evaluated for baseline CTC and ARv7. Interestingly, 75% of patients experiencing a progression at month 3 were classified as ARv7 positive at baseline. Conclusions: The study met its primary endpoint showing enzalutamide is an active treatment option for men with mCRPC and visceral disease in both pre or post-docetaxel setting. CTCs status combined with ARv7 detection could be useful to personalize treatments. Clinical trial information: NCT03103724.

299 Background: Bone is one of the most common site of metastasis occurring in 30% of metastatic renal cell carcinoma (mRCC) patients (pts)3,4. Skeletal metastases from mRCC are usually osteolytic and associated to high rate of morbidity and complication through skeletal related events (SRE). Bone-targeted therapies (BTT) such as zolendronic acid (ZOL AC) and denosumab (Dmab), shown to decrease the time-to-first and subsequent SREs12. Osteonecrosis of the jaw (ONJ) is a rare but potentially serious adverse event associated with BTT. It occurs in 1-2% of pts treated with BTT and in 10-17% of mRCC pts treated with ZOL AC or Dmab. Vascular endothelial growth factor-Tyrosine kinase inhibitors (VEGF-TKI) represent the backbone treatment for mRCC. Nevertheless, it is unclear whether the association of DMAB and ZOL AC to VEGF-TKITTagents could be associated to higher incidence of ONJ. Methods: We retrospectively collected data, from 2 Italian referring centers for mRCC, about 74 pts with bone metastases from mRCC who received, concurrently or sequentially to VEGF-TKI or immune-oncology (IO), AC ZOL and DMAB from January 2013 to January 2020. All pts provided informed consent for inclusion in the study. Results: All pts received VEGF-TKI as first line treatment. 17 pts received AC ZOL whereas 57 received DMAB. All pts received odontological consultation and orthopantomography before start BTT. The median time of Dmab and AC ZOL exposure was 11.6 months. ONJ occurred in 10/74 pts (7.4%): 6/10 pts were on first line treatment and 4/10 on second line. Treatments administered at the time of ONJ diagnosis were nivolumab (1/10), cabozantinib (2/10), sorafenib (1/10), sorafenib (1/10), sunitinib (4/10) and one pts was off therapy. Conclusions: In this real-life Italian population, treatment with BTT in mRCC pts treated with VEGF-TKI inhibitors and IO is associated to higher incidence of ONJ compared to previous report of pts treated with BTT for bone metastasis and lower compared to previous reports in mRCC. Despite the retrospective collection, we provided one of the largest sample of pts treated concurrently with VEGF-TKI or IO and BTT. Physicians should be careful in the use of BTT combined with other treatments in mRCC pts.

320 Background: The multikinase inhibitor cabozantinib (Cabo) is an effective treatment option for metastatic renal cell carcinoma (mRCC). However, data on the optimal sequencing of Cabo and other available therapies are lacking. In particular, the strategy of continuing Cabo administration after disease progression (PD) has never been investigated yet. In light of its ability of inhibiting MET and AXL, which are implied in VEGFR acquired resistance, the hypothesis of a prolonged efficacy in slowing tumor growth, despite first radiological PD, is worth to be investigated. Methods: We conducted a retrospective multicenter study of mRCC patients (pts) treated with oral Cabo as second or subsequent line between 2014 and 2020 in 11 Italian Oncology units. Our study population included pts treated beyond RECIST first PD due to the clinical benefit and tolerance to therapy demonstrated. As a control group we analyzed pts treated with other therapies (thyrosin-kinase inhibitors (TKIs), everolimus, nivolumab or other) after first radiological PD with Cabo. Our aim was to evaluate the post-progression outcome according the two treatment strategies: Cabo beyond PD or other subsequent therapy. Results: 89 pts were included in the analysis: 45 pts received Cabo beyond PD and 44 another therapy: 22 pts nivolumab, 7 everolimus, 6 sorafenib and the others lenvatinib plus everolimus, sunitinib, HD-IL2, pazopanib or axitinib. The median age of all pts was 61.6 years (22.7-83.2) and 77.5% were male. 40.4% and 31.5% of pts had received one or two prior treatment lines, respectively; the remaining 28.1% received Cabo > 3 line. At Cabo start, 83.9% were intermediate-poor risk according IMDC score (77.8% in CABO beyond PD and 90.5% in the control group) and the most common metastatic sites were lung (76.4%), lymph nodes (69.7%), bone (56.2%), liver (30.3%) and brain (14.8%). The objective response rate to Cabo before PD was significantly higher in pts continuing Cabo beyond PD than in those who were treated with other after first radiological PD (46.7% vs 25%, p = 0.03) and a longer but not statistically significant PFS was observed (median 8.1 vs 5.9 months, p = 0.377). Moreover, the median number of prior therapy lines was significantly higher for pts who were treated with Cabo beyond PD than other (2 vs 1, p = 0.016). Median duration of treatment with Cabo beyond PD was 6.4 months. In addition, continuing Cabo beyond PD was associated with a significantly better post-progression overall survival (OS) than switching to other therapy at PD (median OS 16.9 vs 13.2 months, Hazard Ratio 0.66, 95%CI 0.48 – 0.92, p = 0.011). Conclusions: This study showed a longer post-progression OS in pts continuing Cabo beyond PD than in those who switched to another therapy. With the limitations of a retrospective analysis, this is the first evidence suggesting that maintaining Cabo beyond PD is an effective strategy in pts with mRCC.

319 Background: Nivolumab is approved in the second or further line of treatment for patients with metastatic renal cell carcinoma (mRCC); cabozantinib is approved in a similar setting of patients. Unfortunately, no evidence is currently available regarding the best treatment option after disease progression to both nivolumab and cabozantinib. The aim of this study is to compare the treatment choices after progression to nivolumab and cabozantinib including patients followed in best supportive care (BSC) or active therapy. Methods: In this retrospective observational study, we selected 42 patients from 8 Italian cancer centers. Enrolled patients had progressed to both nivolumab and cabozantinib and subsequently referred to active treatment or BSC. Primary endpoint of the study was the OS of patients on active treatment versus BSC. Secondary endpoints were ORR, PFS and OS of patients on active treatment who received sorafenib versus everolimus. Results: The median age was 65 years, 76.2% were male. The majority of patients had undergone nephrectomy (78.6%), had clear cell histology (83%) and were at intermediate-poor risk at the diagnosis (85.7%). The most frequent site of metastatic disease in the general population and in patients referred to BSC was the lung (73.8% and 88.9%, respectively). For patients referred to active treatment, the most frequent site of metastasis was bone (70.8%). Sunitinib (71.4%), nivolumab (64.3%), and cabozantinib (54.7%) were the most commonly used drugs in the I, II and III lines of treatment, respectively. After progression to both nivolumab and cabozantinib 42.9% of patients were referred to BSC, while 57.1% received active treatment (28.6% everolimus, 16.7% sorafenib, 4.8% sunitinib, 4.8% IL2-HD, 2.4% lenvatinib + everolimus). Median OS was 13 (95% CI: 4-NR) and 3 months (95% CI: 2-4) in patients on active treatment versus BSC ( p=0.001). Patients treated with sorafenib had better disease control when compared with those treated with everolimus (SD 71.4% versus 16.7%, PD 14.3% versus 58.3%; p=0.03), but no significant advantage in terms of PFS (5 versus 3 months, 95% CI: 2-6 versus 2-5; p= 0.5) and OS (NR versus 13 months, 95% CI: 3-NR versus 2-NR; p=0.2) was observed. Conclusions: After treatment with both nivolumab and cabozantinib, when possible, the choice of an active treatment seems to produce an OS advantage when compared with BSC. However, although sorafenib seems to demonstrate better results, we cannot indicate which is the drug of choice, as no significant advantage was shown in terms of OS or PFS from the comparison between sorafenib and everolimus. The limitations of this study are given by the size of the sample examined and its retrospective nature. Further studies are needed to confirm whether active treatment choice is associated with improved OS.

e17088 Background: Immuno-oncology (IO) treatment demonstrated to improve Overall Survival (OS) in metastatic renal cell carcinoma (mRCC). The prognostic impact of previous citoreductive nephrectomy (CN) and radical nephrectomy with curative intent in patients (pts) treated with IO is not well defined. Methods: 229 eligible pts, with a least one radiological assessment of response according to the RECIST 1:1 criteria, were retrospectively collected from 16 Italian referral centers. Baseline characteristics, outcome data including progression-free survival (PFS) and OS were collected. Kaplan-Meier method and log-rank test were performed to compare PFS and OS between groups. Results: 153(66.8%) pts received IO as second line, 61(26.6%) as third line and 15(6.6%) pts as further line. 54 pts (23.6%) were good risk, 144(62.9%) were intermediate and 31(13.5%) were poor risk according to IMDC score. 189(82.5%) pts underwent nephrectomy (of them 72(32.4%) pts had synchronous metastatic disease and underwent CN), while 40(17.4%) pts did not. Nephrectomy was performed before IO treatment. ECOG PS, at the beginning of IO, was 0 for 167 pts (72.9%), the other 62 (27.1%) had ECOG PS 1 or 2. At a median follow up time of 17.5 months (mo), 13 (5.7%) pts are still in treatment while 216 (94.3%) experienced progression. 81 (35.3%) pts were treated after IO progression with mTOR and VEGFR inhibitors. 63 (27.5%) pts continued IO beyond progression. G3-G4 iAE were reported in 46 pts (20%). Median IO-PFS was 4.5 months in pts who did not undergo nephrectomy and 2.9 mo in pts who did (HR log rank 0.713, 95%CI 0.4788 to 1.063; p= 0.0582). Median IO-OS was 18.4 mo in pts who underwent nephrectomy and 10.3 mo in pts who did not (HR log rank 1.915, 95%CI 1.118 to 3.281; p= 0.0024). The difference in OS was irrespective of the IMDC criteria and the lines of treatment. Conclusions: In our real world experience, in mRCC pts treated with IO, previous nephrectomy was associated with a better outcome in terms of OS with all the limitations of a retrospective collection.

4077 Background: In the TRIBE2 study molecularly unselected and untreated mCRC patients were randomized to receive FOLFOXIRI/bevacizumab (bev) followed by the same agents after disease progression (PD) or FOLFOX/bev followed by FOLFIRI/bev after PD. We performed a comprehensive NGS analysis of samples from randomized patients in order to investigate the prognostic impact of tumor mutational load (TML), its additional value with respect to the assessment of microsatellite instability (MSI), and the overall prevalence of potentially actionable alterations. Methods: Tumor DNA was obtained from formalin-fixed, paraffin-embedded blocks from primary tumors of 296 (44%) out of 679 randomized patients and underwent NGS analysis using the Caris MI TumorSeek panel, assessing 592 genes. TML was defined low, intermediate or high if < 7, 7-16 or > 16 mutations/Mb were found. MSI status was determined both by NGS and by IHC. Results: TML and MSI were successfully determined by NGS in 224 (76%) cases. NGS and IHC results were concordant in 221 (99%) cases. TML was low, intermediate or high in 56 (25%), 157 (70%) and 11 (5%) cases, respectively. When compared with TML low and intermediate tumors, TML high were more frequently right-sided (p = 0.013), mucinous (p < 0.001) and MSI-high (p < 0.001). TML high tumors were MSI-high or MSS in 8 (73%) and 3 (27%) cases, respectively. Two out of 3 TML high and MSS tumours showed a pathogenic POLE mutation (p.S459F and p.P286R). The other TML high, MSS and POLE wt tumor was dMMR at IHC (loss of MSH6 expression) and showed a pathogenic MSH6 mutation (p.F1040fs). As compared with low and intermediate TML, high TML was associated with longer PFS (median PFS: 17.3 vs 10.6; HR: 0.54 [95%CI: 0.35-1.09], p = 0.098) and OS (median OS: not reached vs 23.7: HR: 0.45 [95%CI:0-28-1.13], p = 0.106). No interaction effect between TML and treatment arm was observed, and no difference between TML low and intermediate tumors was reported in terms of baseline characteristics and prognosis. Actionable alterations ( HER2 mutations [N = 2] and amplifications [N = 4], KRAS G12C [N = 10] and BRAF V600E mutation [N = 39]) were found in 55 (19%) out of 296 cases. No NTRK/ROS/ALK or MET amplification was found. Conclusions: TML high tumors are not limited to MSI-high ones but showed POLE or MSH6 somatic mutation and shower longer PFS and OS. No differences are reported between TML low and intermediate tumors. Molecular alterations predictive of benefit from targeted strategies currently available are detectable only in a small percentage of mCRCs.

e24150 Background: A large proportion of patients with cancer suffer from Breakthrough cancer pain (BTcP). Several unmet clinical needs concerning BTcP treatment, like optimal opioids dosage, are being investigated. We explored with an unsupervised learning algorithm whether distinct subtypes of BTcP exist and whether they can provide new insights into clinical practice. Methods: We used partitioning around medoids algorithm on a large dataset of patients with BTcP previously collected by the IOPS group in order to identify possible subgroups of BTcP; the input of the algorithm consisted of different BTcP features, like its duration or its intensity. Silhouette statistics was used to pick an optimal number of clusters. Resulting clusters were analyzed in terms of BTcP therapy satisfaction, clinical features and usage of basal pain and rapid onset opioids. Opioids dosages were converted to a unique scale and BTcP-opioids-to-basal-pain-opioids ratio (OpR) was calculated for each patient. Polynomial logistic regression was used to catch non-linear relationships between therapy satisfaction and opioids usage. Results: The cohort comprised 4016 patients with controlled basal pain and suffering from BTcP. Our algorithm identified 12 distinct BTcP clusters. Optimal OpRs differed across the clusters, ranging from 15% to 50%. In the whole cohort, OpR was more clearly associated with therapy satisfaction compared with BTcP opioids or basal pain opioids alone. The majority of the clusters were linked to peculiar association of certain drugs with therapy satisfaction or dissatisfaction. A free online tool was created for new patients cluster computation ( https://mancapaolo.shinyapps.io/UCBM_BTcPclusters/ ) in order to validate these clusters in future studies and to provide a possible, handy indications for personalized BTcP therapy. Conclusions: This work proposes a classification for BTcP and identifies subgroups of patients with unique efficacy of different pain medications. This work supports the theory that the optimal dose of BTcP opioids depends on the dose of basal opioids and identifies novel values, possibly useful for future trials.

4082 Background: Right- (R) and left-sided (L) mCRCs exhibit different clinical and molecular features. Several retrospective analyses showed that the survival benefit of anti-EGFR-based tx is limited to RAS/BRAF wt L-sided mCRC pts, which a larger effect in the first-line setting. Few data are available concerning the anti-EGFR efficacy according to primary tumor site in third line. Methods: Pts affected by RAS/BRAF wt mCRC treated with third-line anti-EGFR-based tx or R/T were retrospectively collected. The objective of the analysis was to compare tx activity and efficacy according to tumor site. Primary endpoint was PFS; secondary endpoints were OS and RR. PFS and OS analyses were performed using Kaplan-Meier method, and survival curves were compared using the log-rank test. RR was evaluated according to RECIST criteria and it was compared in the two groups using Fisher’s exact test. Statistical significance was set at p = 0.05 for a bilateral test. Univariate and multivariate analyses for PFS and OS were performed. Results: A total of 76 RAS/BRAF wt mCRC pts, treated with third-line anti-EGFR-based tx or R/T, were enrolled. Of those, 19 (25%) pts had R-sided tumor (9 pts received anti-EGFR tx and 10 pts received R/T) and 57 (75%) pts had L-sided tumor (30 pts received anti-EGFR tx and 27 pts received R/T). As shown in the table, a significant PFS and OS benefit in favor of anti-EGFR tx vs R/T was observed in L-sided pts, while no difference both in PFS and OS was observed in R-sided pts. RR was significantly higher in L-sided pts treated with anti-EGFR vs R/T, no difference was shown in R-sided pts. At the multivariate analysis, tx regimen was indipendently associated with PFS in L-sided pts, but not in R-sided pts. Conclusions: Our study confirmed the results deriving from the retrospective analysis of the phase III study 20020408. Our results demonstrated a different benefit from third-line anti-EGFR tx according to primary tumor site, confirming the role of L-sided tumor in predicting benefit from third-line anti-EGFR vs R/T, while no difference was observed in R-sided tumors. [Table: see text]

752 Background: Biomarkers to select mRCC patients most likely to benefit to immune-checkpoint inhibitors are still needed. The ongoing retrospective multicentre Meet-URO 15 (I-BIO-REC) study evaluates the prognostic role of peripheral blood cells in mRCC patients treated with nivolumab. Methods:The primary endpoint of the study was median overall survival (mOS) according to bNLR. Complete blood count was collected at the first four cycles of nivolumab. NLR was defined as the ratio of neutrophil to lymphocyte (cutoff = 3) and ΔNLR the difference between NLR at 2nd cycle and bNLR (median used as cutoff = 0.3). Here we reported preliminary analyses on bNLR and DNLR. Results: From May 2016 to January 2019 189 patients started nivolumab as 2nd (62%), 3rd (25%) and > 3rd (13%) line. Median age was 69 years, 67% were male and 87% had clear cell histology. Baseline IMDC group was favorable in 26%, intermediate in 63% and poor in 11%. Lymph-nodes, visceral and bone metastases were present in 55%, 92% and 37%. mOS and progression-free survival (PFS) were 30.5 months and 9.5 months. Overall response rate (ORR) and disease control rate (DCR) were 28% and 57%. bNLR was available in 162 patients: bNLR < 3 (52%) correlated with statistically significant longer PFS [11.5 vs 5.6 months; HR 1.61 (1.09-2.39), p = 0.017] and OS [NR vs 22.4 months; HR 2.61 (1.53-4.46), p < 0.001], with similar ORR (32% vs 32%) but higher DCR (66% vs 55%) compared to NLR ≥ 3. ΔNLR was available in 136 patients: ΔNLR < 0.3 (50%) correlated with statistically significant longer PFS [17.1 vs 8.5 months; HR 1.57 (1.02-2.43) p = 0.04] and OS [medians not reached; HR 1.91 (1.04-3.51) p = 0.038], with similar ORR (39% vs 32%) but higher DCR (73% vs 56%) compared to ΔNLR ≥ 0.3. Univariate and multivariate analyses adjusted for IMDC group, line of therapy and metastatic sites, confirmed the statistically significant correlation between ΔNLR with PFS and OS and NLR with OS but not with PFS. Conclusions: Preliminary analyses of our study showed a prognostic role of bNLR and early ΔNLR in mRCC patients treated with nivolumab.

751 Background: Biomarkers to select mRCC patients most likely to benefit to immune-checkpoint inhibitors are still needed. The ongoing retrospective multicentre Meet-URO 15 (I-BIO-REC) study evaluates the prognostic role of peripheral blood cells in mRCC patients treated with nivolumab. Methods:The primary endpoint of the study was median overall survival (mOS) according to baseline neutrophil to lymphocyte ratio (NLR), but here preliminary analyses on baseline LMR and SII (secondary endpoints) are reported. LMR was defined as the ratio of lymphocyte to monocyte (cutoff = 3) and SII as platelet x neutrophil/lymphocyte (cutoff = 1375). Results: From May 2016 to January 2019 189 patients started nivolumab as 2nd (62%), 3rd (25%) and > 3rd (13%) line. Median age was 69 years, 67% were male and 87% had clear cell histology. Baseline IMDC group was favorable in 26%, intermediate in 63% and poor in 11%. Lymph-nodes, visceral and bone metastases were present in 55%, 92% and 37%. mOS and progression-free survival (PFS) were 30.5 months and 9.5 months. Overall response rate (ORR) and disease control rate (DCR) were 28% and 57%. LMR was available in 150 patients: LMR ≥ 3 (44%) correlated with statistically significant longer OS [NR vs 26.8 months, HR 0.50 (0.29-0.88); p = 0.016] but not PFS (10.3 vs 9.9 months, HR 0.87 (0.58-1.31); p = 0.5) with similar ORR (34% vs 33%) and DCR (60% vs 63%) compared to LMR < 3. SII was available in 162 patients. SII < 1375 (82%) correlated with statistically significant longer PFS [11.5 vs 3.4 months; HR 2.16 (1.36-3.43), p = 0.001] and OS [NR vs 9.5 months; HR 3.87 (2.21-6.78), p < 0.001] with higher ORR (35% vs 20%) and DCR (65% vs 40%) compared to SII ≥ 1375. Univariate and multivariate analyses adjusted for IMDC group, line of therapy and metastatic sites, confirmed the statistically significant correlation between SII with PFS and OS, but not for LMR. Conclusions: Preliminary analyses of our study showed a prognostic role of baseline SII, while it is uncertain for LMR in mRCC patients treated with nivolumab.

691 Background: In metastatic renal cell carcinoma (mRCC), immune-oncology (IO), alone or in combination, (IO-IO or IO-TKI) has changed the therapeutic scenario. Few real-world data are available about safety and outcome after IO progression. Methods: Baseline characteristics, outcome data including progression-free survival (PFS) and toxicities were retrospectively collected from 162 eligible pts treated in 16 Italian referral centers adhering to the Meet-Uro group and progressing to IO. Results: 111 pts (68,5%) were treated after progression to IO. 142 (87.6%) pts received IO as second line, 5 pts as first line and 16 pts as further line. Subsequent therapy included cabozantinib (n = 79, 48.0%), everolimus (n = 11, 6.7%), sunitinib (n = 6, 3.7%) and others (n = 15, 9.25%). Median IO-PFS was 4 months (95%CI 3.1-4.8) with no difference in pts pretreated with pazopanib or sunitinib (4 months (95%CI 2.4-5.5) vs 3,9 months (95%CI 2.9-4.9) p = 0.5). PFS tends to be longer in pts reporting adverse events of any grade (5.03 (95%CI 3.8-6.1) vs 2,99 (95%CI 2.4-3.5) months p = 0.004) or without nephrectomy (4.1 vs 2.9 months p = 0.071). Median PFS, in pts treated post-IO, was 6.5 months (95%CI 5.1-7.8). In term of best response, 55 pts (49%) had stability of disease/partial response and 29 pts (26%) had progressive disease, for the other pts treatment is still ongoing. Pts with ECOG PS 0 at progression to IO, had longer PFS, 11 months (95%CI 5.7-17.5) as well as those treated with cabozantinib (7.6 months, 95%CI 5.2-10.1) compared to everolimus, (3.2 months, 95%CI 1.8-4.5) or other drugs (4.3 months, 95%CI 1.3-7.4) p = 0.001. All grade adverse events were reported in 83 pts (74%) with G3-G4 adverse events in 39 pts (35%). Median overall survival, from first line, was 41,1 months (95%CI 30.4-51.8). Conclusions: In our real world experience after progression to IO, most pts received VEGF-TKI and mTOR inhibitors that showed to be active and safe choices. Cabozantinib was associated with a longer mPFS.

3540 Background: Retrospective analyses and phase 2 studies suggest that administering an anti-EGFR in advanced lines may be effective in mCRC pts who achieved benefit from a 1st-line anti-EGFR containing regimen. The identification of clinical features associated with benefit from anti-EGFR re-treatment (re-tx) in pts experiencing PD during 1st-line anti-EGFR (rechallenge) or after its interruption (reintroduction), is a major clinical need. Methods: A real-life data-base including a total of 5530 pts treated at 6 insitutions from December 2010 to October 2018 was queried. Pts retreated with anti-EGFRs, with RAS/ BRAF wild-type status on tissue samples, who had received a 1st-line anti-EGFR-based tx with at least SD as best response, and at least one further line of therapy before anti-EGFR re-tx, were included. The association with RECIST response (RR), PFS and OS was investigated for the following variables: RR (PR or CR vs SD) and PFS during 1st-line; time from the last anti-EGFR administration to 1st-line PD (i.e. re-introduction vs rechallenge); reason for anti-EGFR discontinuation in 1st-line (PD vs. other); number of anti-EGFR-free lines of therapy before re-tx; anti-EGFR free interval (time between the last anti-EGFR administration in 1st-line and the time of re-tx); primary tumor side; time from the diagnosis of metastatic disease to re-tx (≥ vs. < 18 mos). Results: Data from 86 patients were retrieved, 56 (65%) and 30 (35%) received anti-EGFR rechallenge or reintroduction, respectively. Median anti-EGFR free interval was 15.1 mos. The RR during re-tx was 19.8%, with a DCR of 46.5%. Median PFS and OS were 3.6 and 10.2 mos, respectively. No significant association of investigated features with RR and PFS was observed. No differences in RR or PFS were observed among patients receiving anti-EGFR re-tx as rechallenge or reintroduction (20.4% vs 23.1%, p = 0.99; median PFS: 3.49 vs 4.97 mos, p = 0.61). Patients with left-sided tumors had longer OS (HR: 0.50, 95%CI: 0.26-0.93, p = 0.005). Conclusions: Clinical factors that are generally believed to affect the efficacy of anti-EGFR re-tx are not confirmed in our series. Therefore, clinicians should not rely on those characteristics in their decision-making on anti-EGFR re-tx, and adequate studies for implementing liquid biopsy in clinical practice are urgently needed.

3508 Background: In the phase III TRIBE study FOLFOXIRI/bev significantly improved Response Rate (RR), PFS and OS when compared with FOLFIRI/bev as initial treatment of mCRC. However, the actual advantage by the triplet could be lower when compared with a pre-planned sequential strategy of doublets (FOLFOX, FOLFIRI). TRIBE2 (NCT02339116) is a phase III trial in which unresectable mCRC pts were randomized 1:1 to FOLFOX/bev followed by FOLFIRI/bev after PD (arm A) or FOLFOXIRI/bev followed by the reintroduction of the same regimen after PD (arm B). A pre-planned interim analysis showed a significant advantage for arm B in terms of PFS2, primary endpoint of the study, defined as the time from randomization to PD on any treatment given after first PD or death (PD2). Methods: The study had 80% power to detect a HR for PFS2 of 0.77 in favor of arm B with an overall 2-sided-α error of 0.05 (0.0131 and 0.0455 for the interim and final analyses, planned at 303 and 466 PFS2 events, respectively). Secondary endpoints included RR, 1st-PFS, i.e. the time from randomization to the first evidence of PD or death (PD1), 2nd-PFS, i.e. the time from PD1 to PD2, and OS. Results: From February 2015 to May 2017, 679 pts (arm A/B: 340/339) were enrolled in 58 Italian sites. Main pts’ characteristics were (arm A/B): right side 38%/38%, synchronous mets 89%/89%, RAS mutant 65%/63%, BRAF mutant 10%/10%. At a median follow up of 30.6 mos, 514 (arm A/B: 272/242) PD2, 594 (arm A/B: 303/291) PD1 and 408 (arm A/B: 217/191) OS events were collected. A significant advantage by upfront FOLFOXIRI/bev was confirmed in terms of PFS2 (19.1 vs 16.4 mos, HR 0.74, 95%CI 0.62-0.88, pst-PFS (12.0 vs 9.8 mos, HR 0.75, 95%CI 0.63-0.88, pnd-PFS (6.5 vs 5.8 mos, HR 0.76, 95%CI 0.59-0.97, p=0.024). Conclusion: Upfront FOLFOXIRI/bev followed by the pre-planned reintroduction of the same agents after PD provided a statistically significant and clinically relevant PFS2 and OS benefit when compared with the pre-planned sequential administration of FOLFOX/bev and FOLFIRI/bev in unresectable mCRC patients. A median OS of 27.6 mos was reached despite the high percentage of pts with poor prognostic features ( RAS and BRAF mutations, right side, synchronous mets). Clinical trial information: NCT02339116.

e14075 Background: Unlike chemotherapy, the optimum treatment duration with Immune checkpoint inhibitors (ICIs) is not clearly established. The aim of this study was to assess the outcome of patients (pts) who discontinued immune-based therapies for any reason except progressive disease. Methods: We conducted an observational, retrospective analysis of 46 consecutive pts with advanced cancer who received ICIs as clinically indicated, at eight Italian institutions. Tumor response to treatment was defined according to RECIST. Median overall survival (OS) and the 95% confidence interval (CI) were estimated with the Kaplan -Meier method. Results: 46 pts (median age 68 years [range 41-86]; male: 65.2%) with advanced cancer (n.39 non-small-cell lung cancer, n.15 renal cell carcinoma and n.2 melanoma) were treated with ICIs: 44 pts received programmed death 1 (PD-1) inhibitors (n.31 nivolumab, n.13 pembrolizumab) and 2 pts programmed death ligand 1 (PD-L1) (n.1 durvalumab, n.1 atezolizumab). A median of 8 cycles were administered [range 1 to 52]. 36 pts discontinued ICIs due to toxicities (diarrhoea, pneumonitis, hepatotoxicity) and 10 pts for reasons non immune-related. The median progression free survival (PFS) from the beginning of ICIs was 12.4 months (mo) [95% CI: 8.2-16.6] and the median OS was 20.0 mo (95% CI: 11.8-28.2). Median PFS from discontinuation of therapy was 5.0 mo [95% CI: 2.7-7.3] and median OS was 16.1 mo (95% CI: 5.4-26.8). Best response achieved according RECIST criteria were: 1 complete response (CR), 18 partial response, 21 stable disease (SD), 2 progressive disease (PR) and 3 non evaluable (NE). During interruption of ICIs 1 pts achieved a PR. Conclusions: This study shows the activity of ICIs, in terms of outcome and durable immune-response, in pts with advanced cancer even after treatment discontinuation.

2559 Background: In the preliminary analysis of the FAMI-L1 study, we found a significant association between family history of cancer (FHC) and better clinical outcomes with anti-PD1/PD-L1 inhibitors. Methods: We retrospectively evaluated advanced cancer patients treated with single agents PD1/PD-L1 inhibitors. Patients were categorized as follow: FHC-high (in case of at least one cancer diagnoses in both straight and collateral family line), FHC-low (in case of a cancer diagnoses in only one family line) and FHC-negative. FHC was collected till the second degree of relatedness. Results: Between September 2013 and May 2018, 772 consecutive patients were evaluated. Median age was 68 years; male/female ratio was 521/251. Primary tumors were: NSCLC (58.3%), melanoma (22.1%), renal cell carcinoma (16.6%) and others (3%). 114 patients (14.9%) had ECOG-PS ≥ 2. 341 patients (44.3) were FHC-positive: 268 of them (34.75) were FHC-low while 74 (9.6%) were FHC-high. FHC-high patients had a significantly higher incidence of irAEs compared to FHC-negative (55.4% vs 35.6%; p = 0.0012) and to FHC-low (41.4%; p = 0.0323). No significant differences were found in terms of ORR among subgroups (data not shown). At median follow-up of 15.8 months, median PFS was 9.1 months (95%CI: 8.1-10.4; 452 events) and median OS was 19.7 months (95%CI: 15.7-24.4; 436 censored). No significant differences were found regarding PFS (data not shown). Median OS of FHC-high patients was 31.6 months (95%CI: 26.2-31.6; 50 censored patients), which was significantly longer than 18.2 months (95%CI: 14.7-21.3; 229 censored patients) of FHC-negative patients (HR = 0.60 [95%CI: 0.39–0.92), p = 0.0213). No significant differences in terms of OS were found between FHC-high/low patients (data not shown). After adjusting for primary tumor, sex, treatment-line, number of metastatic sites and ECOG-PS, FHC-high was confirmed an independent predictor of longer OS compared to FHC-negative (HR: 0.57 [95%CI: 0.37-0.88], p = 0.0098). Conclusions: FHC-high seems to be an independent predictor for longer OS in cancer patients treated with anti-PD-1/PD-L1. DNA damage and response (DDR) genes alterations may underlie that results.

11053 Background: Dexrazoxane (DEX) is indicated as a cardioprotective agent for patients receiving doxorubicin, who are at increased risk for cardiotoxicity. Concerns have been raised on the use of DEX, particularly in the adjuvant setting, because of the risk of interference with the antitumor effect of doxorubicin. Two meta-analyses in metastatic breast cancer have rejected this hypothesis, but have shown an apparent increase in the severity of myelosuppression when DEX is used. No data in soft-tissue sarcoma (STS) patients is available, so far. Here, we retrospectively analyzed a cohort of our Institute database to assess whether the addition of DEX causes more bone marrow suppression in STS patients receiving Anthracycline-Ifosfamide (AI) combination in perioperative and advanced setting. Methods: 133 patients who received AI between January 2006 and December 2017 were included. 46 of them received DEX concurrently with the AI treatment. Hospital records were reviewed and available for all patients (the accessibility of all the data was an inclusion criterion). Compared to the non-DEX group, patients who received DEX were more frequently treated in the context of a perioperative setting (respectively 27.3 vs 38.8%). No other differences in terms basal patient features were recorded. Significantly, all patients received similar post-medication after each cycle. Results: Compared with the non-DEX group, DEX treatment was associated with significantly higher rates of G3/4 hematological side effects: leucopenia (28.7 vs 56.5%, p value=0.0014); neutropenia (35.6 vs 69.6%, p value=0.0002); anemia (28.7 vs 41.3%, p value=0.1758); thrombocytopenia (32.1 vs 54.3%, p value=0.0159). Similarly, compared to the non-DEX group, there were more hospitalizations for febrile neutropenia (37.9 vs 63.0%, p value=0.0066) and dose reductions (19.5 vs 39.1%, p value=0.0221) in the DEX group, above all in perioperative setting (15.6 vs 58.3%, p value=0.0085); but no significant difference in the incidence of treatment delays or interruption. Conclusions: Adding DEX to Anthracycline-based chemotherapy in soft-tissue sarcoma patients leads to higher rates of bone marrow suppression in all blood components, as well as more febrile neutropenia events, and dose reductions.

4075 Background: In the ePHAS study we analyzed three eNOSpolymorphisms and at univariate analysis, patients with eNOS-786 -TTgenotype had significantly shorter median Progression Free Survival (PFS) and Overall Survival (OS) compared to those with other genotypes. On the basis of these preliminary results, our aim is to validate in a prospective study this data in patients with HCC treated with sorafenib. Methods: This is a prospective Italian multicenter study, that includes 141 HCC patients receiving sorafenib. We analyzed eNOS-786and itwas analyzed by Real Time PCR in relation to the primary end point (OS). Event-time distributions were estimated using the Kaplan-Meier method and survival curves were compared using the log-rank test. Results: 141 HCC patients (122 males and 19 females), prospectively treated with sorafenib from May 2015 to September 2018 were included. Median age was 69 years (range 28-88 years). 120 patients had Child-Pugh A and 21 had Child-Pugh B7. 43 had BCLC-B and 98 patients had BCLC-C. Atunivariate analysis, we confirmed that eNOS-786 TT genotype were significantly associated with a lower median OS than the other genotypes (8.8 vs 15.7 months, HR 1.69, 95% CI 1.02-2.83 p=0.0424). Following adjustment for clinical covariates (age, gender, etiology, BCLC stage, serum α-FP level, MELD score), multivariate analysis confirmed eNOS- 786 and BCLC stage as the independentsprognostic factors predicting OS (TTvsTC+CC; HR: 2.39, 95% CI 1.14-5.03 p=0.0211; C vs B;2.23, 95% CI 1.44-4.77 p=0.039). Conclusions: Our prospective study confirms the prognostic role of eNOS-786 in advanced HCC patients treated with sorafenib. Clinical trial information: NCT02786342.

3534 Background: Based on retrospective experiences, gender seems to affect the safety profile of chemotherapy (CT), with a higher incidence of CT-related adverse events (AEs) among females than males. Here we focus on the impact of gender on the toxicity of FOLFOXIRI/bevacizumab (bev) as compared with doublets (FOLFOX or FOLFIRI)/bev in two randomized phase III studies by GONO: TRIBE and TRIBE2. Methods: The risk of experiencing CT-related AEs in males and females was estimated in univariable analysis in the overall safety population and according to treatment arms (doublets/bev and FOLFOXIRI/bev). In order to assess the independent weight of gender on the risk of developing AEs, multivariable logistic regression models were built. Results: Among 1187 patients enrolled in TRIBE and TRIBE2 studies, 1176 (684 males, 58%, and 492 females, 42%) were included in the safety population. Overall, women had a significantly higher risk of CT-related AEs, in particular gastrointestinal and hematologic AEs, asthenia and alopecia, independently of the treatment arm. The risk of CT-related AEs was increased with FOLFOXIRI/bev vs doublets/bev independently of gender (p for interaction: 0.329). Notably, among women treated with FOLFOXIRI/bev 50% and 68% experienced any grade of vomiting and nausea, respectively. Conclusions: Female mCRC patients have a higher risk to develop CT-related AEs. In women treated with FOLFOXIRI/bev the high incidence of nausea and vomiting may suggest the need for an intensification of the antiemetic prophylaxis. [Table: see text]

11591 Background: FOLFOXIRI/bev is a valid option as first-line therapy for unresectable mCRC. TRIBE and TRIBE2 trials reported better activity and efficacy of the triplet/bev when compared with doublets/bev at the price of a higher incidence of chemo-related toxicities, including neutropenia (N). Here we aim at providing a detailed description of this adverse event, including the occurrence of febrile neutropenia (FN) and the use of granulocyte-colony stimulating factors (G-CSFs), in order to estimate the clinical relevance of N during FOLFOXIRI/bev. Methods: Safety data of 1175 pts enrolled in the TRIBE and TRIBE2 studies were reviewed. The incidence of N, the incidence and severity of FN, and the use of G-CSF in the triplet/bev and in the doublets/bev arms were compared using the Chi-square or the Fisher exact test as appropriate. Results: Out of 1175 pts included in the final analysis, 586 (49.8%) were treated with FOLFOXIRI/bev. Five pts (0.8%) in the doublets/bev arms and 29 (4.9%) in the triplet/bev arms received a primary prophylaxis with G-CSF. Among other pts, 118 (20.2%) in the doublets/bev arms and 276 (49.9%) in the triplet/bev arms experienced ≥ G3 N (p < 0.001). FN occurred in 25 (4.3%) and 41 (7.4%) cases respectively (p=0.041). Out of 78 FN episodes, 4 (13.3%) out of 30 in the doublets/bev arms and 13 out of 48 (27.1%) in the triplet/bev arms were associated with a poor MASCC score (

TPS731 Background: The immune system plays a crucial role in modulating response to monoclonal antibodies therapy in cancer. Novel immunecheckpoint inhibitors have demonstrated potent efficacy alone and in combinations with cytotoxic agents in several cancers. In this regard, avelumab in combination with cetuximab might be a relevant rechallenge strategy in RAS wild-type (WT) metastatic colorectal cancer (mCRC) patients treated in first-line with chemotherapy (CT) in combination with anti-EGFR drugs and who achieved a complete or partial response. Methods: CAVE Colon is a single arm, multi-center phase II study designed to evaluate the efficacy of avelumab and cetuximab in pre-treated RAS WT mCRC patients. Eligible patients: pathologically confirmed RAS WT mCRC treated with a first-line CT in combination with an anti-EGFR agent with a major response achieved (complete or partial), who have progressed to a second line therapy, and received no prior immunotherapy. Primary endpoint is overall survival, secondary endpoint are overall response rate according to RECIST 1.1, progression free survival and safety profile. The current study seeks to demonstrate a median OS of 11 months (alternative hypothesis) by the experimental combination for comparison with historical median OS 8.0 (null hypothesis) with standard third line treatments, which correspond to an improvement of OS at six months from 40% to 57%. It was estimated that it would be needed to enroll 66 patients to achieve a 80% power with a one-sided 5% level test. The accrual period will be 18 months and the total duration of the study will be 36 months. Considering a potential drop-out of approximately 15% of patients, a total of 75 patients will be recruited. Seven patients have been enrolled and started treatment to date (September 15, 2018) with avelumab 10 mg/kg q14 as a one-hour i.v. infusion and cetuximab at 400 mg/m2 over two-hour and subsequently 250 mg/m2 q 14 as one-hour i.v. infusion until disease progression or unacceptable toxicity. EudraCT number: 2017-004392-32. This study is partially supported by Merck KgA, Darmstadt, Germany. Results: N/A. Conclusions: N/A. Clinical trial information: EudraCT number: 2017-004392-32.

11556Background: Desmoid tumours (DTs) are monoclonal neoplasms with fibroblastic-myofibroblastic differentiation and they represent the most common extra-intestinal manifestation of familial adeno...

12007Background: CRICKET (NCT02296203) was designed to investigate the activity of the rechallenge with cet and iri as 3rd-line treatment in RAS/BRAF wild-type mCRC pts with acquired resistance to ...

TPS405 Background: The most significant morbidity of prostate cancer (PC) is bone metastasis (BM). More than 90% of patients (pts) with metastatic castration-resistant prostate cancer (mCRPC) have radiologic evidence of BM, which are a major cause of death, disability, decreased QoL, and increased treatment cost. Unlike deaths from many other types of cancer, deaths from PC are often due to bone disease and its complications. In vitro data demonstrate a role for taxanes in the regulation of osteoclast formation and function, with a decreased resorption activity. ÊSTAMPEDE study has shown a strong clinical benefit, in term of OS, PFS and skeletal related events (SREs) delay compared with ADT alone, in metastatic hormone-sensitive pts treated with docetaxel (DOC) and ADT. TROPIC Study has shown that cabazitaxel (CBZ) prolongs OS regardless of DOC response in responder, resistant and refractory pts. Some data are available on pain progression, pain response and ECOG PS deterioration but in a unselected ITT population with a low prevalence of only BM disease at baseline, 25% of men had visceral metastasis. No data are available on effects of CBZ on BM and his direct impact on quality of life, bone turnover markers and time to the first SRE events. The aim of CaBone phase II study is to investigate, specifically, the effects on bone disease, bone turnover and on the bone related quality of life of CBZ in mCRPC pts with skeletal involvement without visceral disease. Methods: CaBone is a single arm, prospective, open label, multi center, phase II - GOIM - cooperative study of CBZ 25 mg/m2 q21 plus daily PDN (10 mg) in mCRPC pts with bone mets without visceral disease progressed during or after DOC treatment. Primary endpoint is Bone PFS according to PCWG2 while the Secondary are related on Evaluation of bone disease: Time to SRE, Time to Bone Pain Progression, Bone Pain Response, Time to opiate use for cancer-related pain, Time to deterioration in ECOG PS, Evaluation of Quality of Life and Functional status, Safety and centralized bone turnover markers: ALP, Bone ALP , LDHÊ, Serum CTx, iPTH, 1.25 (OH)2ÊD3. 107 subjects will be enrolled in CaBone study. CaBone is partially supported by Sanofi Genzyme. Clinical trial information: 2016-001253-41.

639 Background: BM mCRCs account around 10% of mCRCs, with a dismal prognosis. Intra-group heterogeneity has been recently studied, however, an extensive prognostic clinical analysis has not been provided yet. Methods: BM mCRCs tested on primary tumor (T) or on metastases (mets) were collected from 13 Italian Oncology Units. A prognostic score was derived by an internal cross-validation procedure: the whole population was splitted in a training (67%) and in a testing (33%) sample; this process was repeated 10 times. Primary endpoint was OS. Multivariate analysis (MA) was performed on each training sample, and covariates with independent prognostic value were included in the scoring system, assigning rounded scores to the covariates. Results: A total of 395 BM mCRC patients were included. At MA, independent prognosticators for OS were ECOG PS (1 vs 0; 2-3 vs 0), Ca19.9 (high vs normal); LDH (≥300 vs low); neutrophil/lymphocyte ratio ( > 3 vs low); T grading (3-4 vs 1-2); liver mets (yes vs no); lung mets (yes vs no); lymphnode mets (yes vs no). Two different scoring systems were built: a «complete» score (0-18) with all significant covariates; a «simplified» score (0-11), selecting only significant clinico-pathological covariates, excluding laboratory values. With «complete» score, proportion of patients with low (0-4), intermediate (5-8) and high (9-18) score was 39%, 46% and 15%, respectively. Median OS was 27.6, 18.7 (HR interm. vs low 1.89, 95%CI 1.25 – 2.86, p = 0.003) and 6.6 months (HR high vs low 4.95, 95%CI 2.89 – 8.47, p < 0.0001), respectively. Similar results were observed adjusting for type of first-line treatment. Median PFS was 11.1, 8.6 (HR interm. vs low 1.36, 95%CI 0.94 – 1.97, p = 0.11) and 4.1 months (HR high vs low 3.50, 95%CI 1.98 – 6.20, p < 0.0001). Similar results were obtained with the «simplified» score. Conclusions: A simple and ready-to-use prognostic score for BM mCRC was developed. The robustness of the internal cross-validation justifies the effort of a validation study. Identification of specific prognostic factors in distinct molecular subgroups is crucial for adjusting exploratory translational analyses and future clinical trial design.

Purpose A high interleukin-1β (IL-1B) and interleukin-1 receptor antagonist (IL-RN) ratio underlies an unfavorable proinflammatory status. Also, it seems to be involved in the mechanisms of cancer cachexia and tumor angiogenesis and metastasis. Two single nucleotide polymorphisms in IL-1B gene (IL-1B-511C/T,IL-1B-31T/C) and a variable number of tandem repeat polymorphisms in IL-RN gene (IL-1RNlong/2) enhance the circulating levels of the two cytokines. The prognostic role of IL-1B/IL-1RN genotypes was investigated in patients with relapsed and metastatic gastric cancer treated with palliative chemotherapy. Patients and Methods Before starting palliative chemotherapy, 123 prospectively enrolled patients supplied peripheral-blood samples for DNA extraction. Survival data were analyzed according to IL-1RN/IL-1B genotypes. Results Forty-two patients showed wild-type genotypes (IL-1RNlong/long, IL-1B-511C/C, and IL-1B-31T/T; group A). Forty-five patients showed the IL-1RN2 polymorphism, with wild-type IL-1B genotypes in seven patients and with IL-1B-511C/T and/or IL-1B-31T/C polymorphisms in 38 patients (group B). The remaining 36 patients demonstrated wild-type IL-1RN, with IL-1B-511C/T and/or IL-1B-31T/C polymorphisms (group C). In group A and B patients, the median progression-free survival (PFS) was 25 and 26 weeks, respectively, and median overall survival (OS) was 42 and 43 weeks, respectively. Group C patients showed worse PFS (median, 16 weeks) and OS (median, 28 weeks) than group A (P = .006 for PFS; P = .0001 for OS) and group B patients (P = .01 for PFS; P = .0001 for OS). The long/T/C haplotype was overrepresented in patients with shortened PFS (P = .001) and OS (P = .0005). Conclusion In patients with advanced gastric cancer, IL-1B polymorphisms showed adverse prognostic influence when coupled with wild-type IL-1RN genotype. These findings deserve further investigation for potential anticancer activity of recombinant IL-RN.

11038 Background: We retrospectively collected data from metastatic Italian GIST patients treated with imatinib or sunitinib reintroduction after progression to conventional three or four lines of therapy. Methods: 82 eligible advanced GIST patients, previously treated with imatinib, sunitinib and regorafenib, were collected in the present analysis from 6 cancer centres. All patients received all three standard kinase inhibitors. Imatinib dose increase as active second line or 800 mg upfront in exon 9 mutant GIST were allowed. Specific mutations were recorded if available (deletion versus others) and correlated with survival and response according to RECIST 1.1 or CHOI criteria. Results: Seventy-four of 82 patients received Imatinib 400 mg as rechallenge, while 8 patients were treated with sunitinib at personalised dose and schedule according to the physician’s choice. Mutational status was available in all patients and in 68 patients details about type of mutation were achievable. The median follow-up was 13 months (range 1-42 months). The median time to progression (TTP) in patients receiving a rechallenge therapy was 5.4 months (95% CI 1.9-13.5) and Overall Survival (OS) was 10.6 months (95% CI 2.8-26.9). Apparently, in this setting a correlation between mutational status and response rate, TTP or OS was not found. On the contrary, considering only exon 11 mutated patients and comparing patients with deletion vs non deleted ones a significant difference was identified both in terms of TTP and OS (respectively, P = 0.04 and P = 0.02). Conclusions: Our retrospective data confirm that the rechallenge of imatinib or sunitinib is a reasonable option in advanced GIST patients after failure of previous treatments. As expected, imatinib is the most frequently prescribed option in the Italian real-life setting, demonstrating a TTP and OS longer than those observed in previous studies. Also the prognostic value of the specific type of exon 11 KIT mutations has been confirmed in our series.

e22517 Background: Since the first steps of its clinical development, trabectedin was noticed to be extremely active against myxoid liposarcoma (MLS), whose pathogenesis seems to be associated to the presence of the t(12;16)(q13;p11) translocation, resulting in the expression of FUS-DDIT3 fusion genes. Therefore, the drug seems to induce a maturation of MLS lipoblasts, with transition of the residual spindle non-lipogenic cells into mature vacuolated lipoblasts. This effect could be prevented by the increase of leptin circulating levels in obese patients. For these reasons we designed this retrospective analysis in order to evaluate the BMI status (measure of total adipose content) as a predictors or efficacy of trabectedin in MLS patients. Methods: Patients were treated in cancer centers with trabectedin at the approved dose of 1.5 mg/m2, given as a 24-hour infusion every 3 weeks. This retrospective analysis was preformed on the basis of clinical charts or databases. For the purpose of this analysis only patient with a BMI > 18.5 were included and an the population divided into two categories: normal weight if BMI < 25, overweight > 25. An analysis of the correlation between BMI and objective response (OR) rate, tumor control (TC) rate (OR+stable disease lasting ≥3 months), progression-free survival (PFS) and overall survival (OS) was performed. Results: 62 adult patients with recurrent MLS were enrolled (M/F: 33/29; median age: 53 ys). All patients were doxorubicin-pretreated. The median BMI in the whole population was 22.5 (range: 1.85 – 29.8). No statistically significant differences were identified in terms of OR or TC. On the contrary, PFS (6.8 vs. 3.7 months; p< 0.026, log rank test) and OS (14.9 vs. 8.3 months; p< 0.0001, log rank test) were significantly prolonged in normal weighted patients vs over weighted patients. Six and 12-months Kaplan-Meier PFS estimates and survival rates at 12, 24 and 36 months were also better in those patients. Conclusions: these results seem confirm a role o adipose content as a predictor of resistance to trabectedin in MLS patients. Further studies are warranted to confirm this preliminary observation and understand the biological mechanisms of this relationship.

e15684 Background: In 2015 we published a paper where we have assessed the outcome of patient with HCC treated with metformin(M)and sorafenib(S). The data show that the concomitant use of S and m was associated with a lower PFS and OS respect for patients receiving S alone. The aim of this study was to validate the prognostic significance of m in patients with HCC treated with S. Methods: 280 patients with HCC consecutively treated with S twice daily between March 2008 and August 2016 were included in the study. Patients who had been taking insulin (I) for at least 5 years at the time of the HCC diagnosis were considered “ patients with diabetes treated with I,” whereas those who had been on m at for at least 5 years when HCC was diagnosed were considered “ patients with diabetes treated with M.” Results: In patients treated chronically with m the treatment with S was associated with a median PFS of 1.9 months (95% CI 1.8-2.3) compared to 3.7 months (95% CI 3.1-4.6) for patients without DM2 and compared to 8.4 months (95% CI 5.3-11.4) for patients treatment chronically with I (P < 0.0001). In patients treated chronically with m the treatment with sorafenib was associated with a median OS of 6.6 months (95% CI 4.6-8.7) compared to 10.8 months (95% CI 9.0-13.1) for patients without DM2 and compared to 16.6 months (95% CI 14.5-25.5) for patients treatment chronically with I (P = 0.0001). Metformin effects on clinical outcome were also investigated in relation to ORR. Patients treated chronically with metformin showed a higher percentage of progression at the first CT re-evaluation than those patients treatment with I and patients without DM2 (75.8% vs. 14.7% vs 38,8%, respectively). Considering the overall population, the risk of progression, was higher in DM2 patients taking m compared with patients without DM2 (HR = 1.91, 95% CI 1.28-2.8,). Regarding the risk of survival, similar results were observed (HR = 1.70, 95% CI 1.14-2.55). Conclusions: These results confirm an increased tumor aggressiveness and resistance to S in patients treated with m cronicaly.Molecular alterations in transporter genes or transcription factors involved in m molecular action and pharmacokinetics could contribute to a different response to these drugs combination.

TPS4601 Background: In the cytokine era cytoreductive nephrectomy (CN) has been shown to increase survival in patients (pts) with metastatic renal cell carcinoma (mRCC). Efficacy of tyrosine kinase inhibitors (TKIs), including first-line sunitinib and pazopanib has been demonstrated. It is unclear if similar survival benefit could be achieved without CN with TKIs since most of pts enrolled into phase III trials had undergone CN. Methods: A total of 270 mRCC pts will be randomized to receiveCN followed by TKIs vs upfront TKIs without CN. Patients will receive pazopanib 800 mg orally daily or sunitinib 50 mg daily, 4 weeks on/ 2 weeks off. The choice of TKI will be done according to investigator’s clinical practice. Primary objective: to compare clinical benefit, as measured by overall survival (OS), provided by CN followed by TKIs vs upfront TKIs in pts with mRCC. Secondary objectives: i) to compare clinical benefit, as measured by progression-free survival (PFS) and response rate (RR) provided by CN followed by TKIs vs upfront TKIs; ii) Safety; iii) Exploratory analyses: evaluation of the predictive role of circulating tumor cells count and circulating tumor DNA at baseline, before and after surgery (in pts undergoing CN), 24 weeks after randomization and at the time of disease progression. Key inclusion criteria: Favorable or intermediate MSKCC or Heng prognostic risk group; histological diagnosis of RCC with a clear-cell component; resectable asymptomatic mRCC with primary tumor in place; up to three different metastatic sites; ≥ 3 metastatic lesions. Key exclusion criteria: Widespread disease ( > or = 4 metastatic organ sites); disease suitable of metastasectomy ( < 3 lesions confined at one organ site). Statistical plan: The sample size was calculated in order to compare 5-year OS between subjects randomized to receive CN followed by TKIs and those randomized to receive upfront TKIs. A total of 191 deaths will yield 80% power to detect a hazard ratio of 1.5 of upfront TKIs vs CN followed by TKIs with an overall type 1 error of 0.05 (two-sided log-rank test). Such a HR corresponds to an increase in the 5-year OS, from an anticipated value of 10% for TKIs to 21.5% for CN followed by TKIs. To date 10/270 pts have been enrolled. Clinical trial information: NCT02535351.

629 Background: Presently few options are available for pts with mCRC who failed standard treatments and prognosis remains grim. MGMT promoter methylation is a frequent and early event in CRC tumorigenesis. This epigenetic silencing is a predictor of response to the alkylating drug TMZ in glioblastoma. Preclinical evidences and a couple of clinical cases showed TMZ activity in pts affected by mCRC with MGMT silencing. We designed a study to evaluate the efficacy and safety of TMZ in pts with refractory mCRC harboring MGMT promoter methylation. While the trial was ongoing three analogous studies, reporting discordant results, were published. Methods: This was a 3-institutional, single arm, phase 2 trial, planned according to a 2-stage Simon’s optimal design. The primary endpoint was ORR. Secondary outcomes included DCR, OS, PFS and safety. A first cohort of 21 pts was accrued: if more than 1 response was observed a second cohort of 20 pts would be enrolled; if 4 or fewer responses were observed by the end of stage two, then no further investigation would be warranted. MGMT promoter methylation was assessed on archival tissue samples by MS-PCR. Patients affected by MGMT methylated mCRC, who failed 2 or more prior treatments, received TMZ, provided by TEVA Pharmaceutical Industries, at a dose of 150-200 mg/mq/day once a day on days 1-5 every 28 days. Results: From July 2012 to June 2016, 225 pts were screened and 80 showed MGMT promoter methylation, among those 42 met the inclusion and exclusion criteria and were enrolled. ORR was 10% with no CR and 4 (10%) PR. SD was achieved in 9 (22%) pts, accounting for a DCR of 32%. At a median FU of 9 months all pts experienced PD and 88% died. Median PFS and OS were 2.6 months (95% CI 2.1-3.2) and 7.1 months (95% CI 5.1-9.2) respectively. Overall, any-grades AEs were reported in 75.6% pts, most of them were G1-2 (84%). The most frequent AE were nausea (56%) and platelet count decreased (39%). 4 pts discontinued study treatment due to AE. No SAE neither toxic death was recorded. Conclusions: The study did not meet its primary endpoint, however an interesting DCR (32%) and 4 PR were achieved. The role of TMZ in mCRC treatment remains still controversial and might warrant further analysis. Clinical trial information: 2012-002766-13.

TPS4584Background: Two randomized trials in the cytokine era clearly showed that cytoreductive nephrectomy (CN) increased life expectancy in metastatic renal cell carcinoma (mRCC) patients (pts). T...

e22537Background: Myxoid liposarcoma (MLS) represents a specific subtype of liposarcoma, one of the most common malignant soft tissue tumors affecting adults. Trabectedin is a DNA-binding agent int...

e23004Background: Cabozantinib (CBZ) is a receptor tyrosine kinase inhibitor with activity against MET, VEGFR2, FLT3, c-KIT, and RET. Pre-clinical studies in models of prostate cancer bone metastas...

TPS3629Background: Chemotherapy plus bevacizumab (bev) is a standard first-line treatment for unresectable mCRC patients. The intensity of the chemotherapy backbone may be modulated from one to thr...

11062Background: Human equilibrative nucleoside transporter 1 (hENT1) is the major gemcitabine transporter into cells. Gemcitabine is an active drug in different sarcoma subtypes including leiomyos...

210 Background: Abiraterone acetate (AA), cabazitaxel (CABA), and enzalutamide (ENZ) are NAs which demonstrated their efficacy in mCRPC pts who have previously treated with DOC. Unfortunately all pts develop a resistance to these drugs and eventually show a progression of disease. Since the androgen receptor machinery remains the ultimate target of NAs in mCRPC post-DOC, some mechanisms of resistance could be common to all NAs. To date, NAs are sequentially administered in the hope of obtaining a cumulative survival benefit. To date it is unknown if the DC duration influence the outcomes of the subsequent treatments. The present study was aimed to retrospectively assess this issue in a large series of mCRPC pts. Methods: We recorded the clinical outcomes of all treatments received after DOC. For the study purpose, we categorized the pts according to the duration of DC (absence of progression) during NA-based second line: DC ≤ 3 mos (primary resistance – PRe); DC from 3.1 to 11.9 mos (intermediate sensitivity – IS); DC ≥ 12 mos (long term disease control – LTDC). Results: A consecutive series of 291 mCRPC pts, median age 71 yrs (46-91), with bone (88%), nodal (53%) or visceral (18%) mets, was collected. All pts received a NA-based as second line after DOC: 160 (55%) received AA, 99 (33%) CABA and 32 (11%) ENZ. PRe was observed in 56 pts (23 AA – 25 CABA – 8 ENZ), IS in 178 (101 AA – 58 CABA – 19 ENZ), LTDC in 57 (36 AA – 16 CABA – 5 ENZ). The third-line clinical outcomes are detailed in the table. Conclusions: From this data, it appears that DC duration may be a prognostic factor, as a probable result of pts/disease selection. In fact, pts progressing more than 12 mos from the start of NA-based second line appear to have more probabilities to live longer, compared to pts progressing earlier, when they receive another NA-based third line therapy. [Table: see text]

e15594 Background: Data about complete remission in patient with metastatic mRCC in TKIs era are extremely limited. We performed a multicenter, retrospective analysis of patients who obtained CR du...

e15246 Background: Satellite repeat RNAs HSAT II belongs to an heterogeneous group of non-coding transcripts, namely long non-coding RNAs. HSAT II transcripts, recently found in pancreatic ductal a...