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BACKGROUND: In mCRC, CEA is used to monitor response to systemic therapy together with imaging. After the end of induction, no major improvement in tumour shrinkage is expected, and the availability of a marker able to predict progressive disease (PD) versus no-PD might allow avoiding CT scans. METHODS: We pooled data from patients with baseline CEA ≥ 10 ng/mL included in TRIBE and TRIBE2 studies with the aim of identifying a threshold for percent increase of CEA from nadir able to predict PD after the end of the induction therapy. RESULTS: In total, 1178 paired CEA and radiological assessments from 434 patients were included. According to the optimal cut-off determined by ROC, a CEA increase of at least 120% from nadir differentiated between PD and no-PD with a sensitivity of 74% and a specificity of 78%, excluding PD in the 92% of radiological assessments and allowing to avoid the 67% of CT scans. However, CEA cut-off of 120% was not able to detect radiological PD in 26% of cases. In order to mitigate this issue, a different clinically relevant threshold was evaluated based on the best sensitivity cut-off. Therefore, using any CEA increase from nadir as a threshold, the sensitivity grew to 93% and only in the 7% of cases the radiological PD was not detected. CONCLUSIONS: In mCRC with baseline CEA ≥ 10 ng/mL, CEA values can accurately predict PD versus no-PD after the end of the first-line induction therapy.

No biomarkers are currently available to predict the efficacy of trifluridine/tipiracil (FTD/TPI) in chemorefractory metastatic colorectal cancer. The multicohort REGOLAND study aims at exploring and validating circulating markers potentially able to predict benefit from regorafenib in this setting.In the retrospective 'regorafenib exploratory cohort', including 105 patients treated with regorafenib, baseline (d1) plasma levels of angiogenesis-related biomarkers and their early modulation after 15 days (d15) of treatment were investigated for correlation with clinical outcome. Based on a pre-specified statistical hypothesis, main retrospective findings were prospectively challenged in the 'regorafenib validation cohort', including 100 patients treated with regorafenib. Prospectively validated putative biomarkers were then assessed in the control 'FTD/TPI cohort', including 93 patients treated with FTD/TPI.In the 'regorafenib exploratory cohort', the early (d15) increase of Angiopoietin-2 (Ang-2) was associated with longer progression-free survival (HR:0.57 [95%CI:0.38-0.88], P = 0.004) and a trend towards longer OS (HR:0.74 [95%CI:0.48-1.14], P = 0.165), than the early decrease. Similar results were prospectively confirmed in the 'regorafenib validation cohort' (HR for progression-free survival:0.72 [95%CI:0.48-1.08], P = 0.095; HR for OS:0.77 [95%CI:0.51-1.16], P = 0.204). No predictive impact was shown for the early modulation of Ang-2 in the 'FTD/TPI cohort'. High baseline Ang-2 levels predict poor prognosis in all the investigated cohorts, independently of other clinical prognostic variables.The early modulation of circulating Ang-2 predicts the efficacy of regorafenib. Baseline Ang-2 plasma levels are an independent prognostic biomarker in chemorefractory metastatic colorectal cancer.

Introduction The consensus molecular subtypes (CMS) demonstrated prognostic value in metastatic colorectal cancer (mCRC). Similarly, a prognostic impact was suggested for the pre-consensus CRCAssigner (CRCA) classifier in early stages. The potential predictive role of these classifiers with regard to the choice of the first-line therapy has not been established. We investigated the prognostic and predictive impact of CMS and CRCA subtypes among mCRC patients treated in the TRIBE2 study. Methods Among 679 randomized patients, 426 and 428 (63%) samples were profiled according to CMS and CRCA classifications, respectively. The prognostic and predictive impact of both CMS and CRCA subtypes was investigated with univariate and multivariate analyses for progression-free survival (PFS), PFS 2 (PFS2), and overall survival (OS). Results Significant associations of CMS and CRCA subtypes with PFS, PFS2, and OS were demonstrated; the CMS classifier confirmed its independent prognostic value in the multivariable model (P value for PFS/PFS2/OS = 0.01/0.07/0.08). The effect of treatment intensification was independent of CMS subtypes (P value for interaction for PFS/PFS2/OS = 0.88/0.75/0.55). A significant interaction effect between CRCA subtypes and treatment arm was demonstrated in PFS (P = 0.02), PFS2 (P = 0.01), and OS (P = 0.008). The benefit of FOLFOXIRI seemed more relevant in the stem-like (PFS, hazard ratio = 0.60; P = 0.03) and mixed subtypes (hazard ratio = 0.44; P = 0.002). These findings were confirmed in a subgroup of patients of the previous TRIBE study. Conclusions We confirmed the independent prognostic role of CMS classification in mCRC independently of RAS/BRAF status. CRCA classification may help identifying subgroups of patients who may derive more benefit from FOLFOXIRI/bevacizumab.

Background Regorafenib is a key agent in metastatic colorectal cancer (mCRC), but no validated factors predicting longer survival are available. Patients and Methods REALITY was a retrospective multicenter trial in regorafenib-treated mCRC patients with overall survival (OS) ≥ 6 months. We aimed to assess the association between clinical parameters and outcome to define a panel identifying long term survivors among regorafenib candidates. Primary and secondary endpoints were OS and progression free survival (PFS), respectively. Statistical analysis was performed with MedCalc (survival distribution: Kaplan-Meier; survival comparison: log-rank test; independent role of significant variables at univariate analysis: logistic regression). Results Hundred regorafenib-treated mCRC patients with OS ≥ 6 months were enrolled. Median OS was 11.5 m (95%CI:9.60-12.96); median PFS was 4.2 months (95% CI:3.43-43.03). The absence of liver progression and of dose and/or schedule changes during the first 4 cycles (mainly for good tolerability) were independently correlated at multivariate analysis with OS (Exp(b)1.8869, P= .0277and Exp(b)2.2000, P = .0313) and PFS (Exp(b)2.1583, P = .0065 and Exp(b)2.3036, P= .0169). Patients with neither of these variables had a significantly improved OS (n = 14, 20.8 months; 95% CI:12.967-55.267) versus others (n = 86, 10 months; 95% CI:8.367-12.167; HR = 0.4902, P = .0045) and PFS (11.3 months, 95%CI:4.267-35.8 vs. 3.9 months, 95% CI:3.167-43.033; HR = 0.4648, P = .0086). Conclusion These 2 factors might allow clinicians to better identify patients more likely to benefit from regorafenib. Toxicity management remains crucial.

Oligometastatic disease (OMD) identifies tumours with limited metastatic spread. OMD definition is not univocal and no data from clinical trials are available about the prognostic effect of OMD in metastatic colorectal cancer (mCRC), the impact of locoregional treatments (LRTs) and the effect of chemotherapy intensification in these patients. The role of tumour burden (TB) in driving therapeutic choices is also debated.We performed a pooled analysis of phase III TRIBE and TRIBE2 studies comparing FOLFOXIRI/bevacizumab (bev) to doublets (FOLFOX or FOLFIRI)/bev. Patients were grouped in OMD versus non-OMD based on the European Society for Medical Oncology definition. Among patients with OMD, those with OMD/low TB were compared with all the others.Of 1187 patients enrolled, 1096 were classified as OMD (N = 312 [28%]) or non-OMD (N = 784 [72%]). Among patients with OMD, 126 (40%) were OMD/low TB. OMD was associated with longer progression-free survival (14.0 versus 10.1 months; p 0.01) and overall survival (38.2 versus 22.0 months; p 0.01). These results were confirmed in multivariable models. The benefit provided by FOLFOXIRI/bev compared with doublets/bev did not differ in accordance with OMD and TB (p for interaction0.05). Patients with OMD underwent LRTs more frequently (p 0.01) and those with OMD/low TB had higher chance to undergo LRTs after the first progression (p 0.01).OMD is a positive prognostic factor in mCRC. The benefit from the upfront treatment intensification is independent of the metastatic spread extent and TB. LRTs should be highly considered in these patients, mainly during the first-line therapy but also at later stages of treatment history in selected cases.

To understand the immune landscape of deficient mismatch repair colorectal cancer (dMMR CRC) tumor microenvironment, gene expression profiling was performed by the nCounter PanCancer Immune Profiling Panel. This study was conducted retrospectively on 89 dMMR-CRC samples. The expression of CD3, CD8, programmed death-1, and programmed death ligand-1 protein was evaluated on a subset of samples by immunohistochemistry, and lymphocyte density was calculated. A subset of deregulated genes was identified. Functional clustering analysis performed on these genes generated four main factors: antigen processing and presentation, with its major histocompatibility complex-II–related genes; genes correlated with the cytotoxic activity of immune system; T-cell chemotaxis/cell adhesion genes; and T-CD4+ regulator cell–related genes. A deregulation score (DS) was calculated for each sample. On the basis of their DS, tumors were then classified as COLD (DS ≤ −3) to select the samples with a strong down-regulation of the immune system and NOT COLD (DS ≥ −2). The COLD group of patients showed a worse prognosis in terms of survival considering all patients (P = 0.0172) and patients with metastatic disease (P = 0.0031). These results confirm that dMMR-CRCs do not constitute a homogeneous group as concerns the immune system activity of tumor microenvironment. In particular, the distinction between COLD and NOT COLD tumors may improve the management of these two subsets of patients.

Background TAS-102 is indicated for patients with metastatic colorectal cancer (mCRC) previously treated with, or not considered candidates for, available therapies. Given the complete inefficacy in half of patients, the lack of predictive factors, the palliative setting, and the financial and clinical toxicity, optimizing the cost-benefit ratio is crucial. The “ColonLife” nomogram allows an estimate of the 12-week life expectancy of patients with refractory mCRC. Materials and Methods We collected data from patients treated at eight Italian centers in the compassionate use program. Baseline characteristics of patients who were or were not progression free at 6 months were compared. The discriminative ability of the ColonLife nomogram was assessed. Among patients who received both TAS-102 and regorafenib, clinical outcomes of the two sequences were compared. Results This study included 341 patients. Six (2%) and 93 (27%) patients achieved response and disease stabilization, respectively. The median progression-free survival (PFS) was 2.4 months with an estimated 6-month PFS rate of 19%; the median overall survival (OS) was 6.2 months. An Eastern Cooperative Oncology Group performance status (ECOG PS) of 0, normal lactate dehydrogenase (LDH), and a time from the diagnosis of metastatic disease of >18 months were independently associated with higher chances of a patient being progression free at 6 months. The discriminative ability of ColonLife was confirmed. Among 121 patients who received both regorafenib and TAS-102, no differences in first or second PFS or OS were reported between the two sequences. Conclusion One out of five patients achieves clinical benefit with TAS-102. ECOG PS, LDH, and time from diagnosis of metastatic disease may help to identify these patients. Excluding patients with very short life expectancy appears a reasonable approach. Implications for Practice Improving the cost-efficacy ratio of TAS-102 in metastatic colorectal cancer is needed to spare useless toxicities in a definitely palliative setting. Eastern Cooperative Oncology Group performance status, lactate dehydrogenase levels, and time from the diagnosis of metastatic disease may help to identify patients more likely to achieve benefit. Properly designed prognostic tools (i.e., the “ColonLife” nomogram) may enable excluding from further treatments patients with very limited life expectancy.

Adenocarcinoma with mucinous histology or mucinous component are histologic subtypes of metastatic colorectal cancers (mCRCs) with limited benefit from cytotoxic agents. Their sensitivity to anti-epithelial growth factor receptors (EGFRs) is not clear.The activity and efficacy of anti-EGFRs was retrospectively evaluated among patients with RAS and BRAF wild-type mCRC with or without mucinous histology or mucinous component. Subgroup analyses according to primary tumor location were conducted.Overall, the study population included 22 mucinous or with mucinous component tumors (11 right- and 11 left-sided tumors) and 83 not mucinous tumors. One patient experienced partial response among mucinous tumors, whereas in the not mucinous group, 42 patients experienced partial response, with an overall response rate of 4% and 51%, respectively (P = .003). The median progression-free survival was 2.8 versus 6.7 months (hazard ratio, 0.28; 95% confidence interval, 0.13-0.59; P .001), and the median overall survival was 6.5 and 16.7 months (hazard ratio, 0.58; 95% confidence interval, 0.33-1.00; P = .022), for the mucinous and not mucinous groups, respectively. Similar results were observed in subgroup analysis according to primary tumor location.Anti-EGFRs may not provide clinically meaningful benefit in mCRCs with mucinous histology or mucinous component compared with those without mucinous component, irrespective of sidedness.

Background: No tools to predict the probability of extrahepatic disease progression (ePD) of initially unresectable, liver-limited metastatic colorectal cancer (mCRC) are currently available. To estimate the likelihood to develop ePD and to identify clinical and molecular factors that could predict extrahepatic progression-free survival (ePFS), we conducted an observational, retrospective, multicentre cohort study. Methods: We retrospectively identified a cohort of 225 patients with initially unresectable liver-limited disease (LLD), treated from January 2004 to December 2017 with first-line doublets or triplet plus a biological agent at two Italian institutions. Results: 173 (77%) patients experienced ePD which occurred within 1, 2 or 3 years from the diagnosis of mCRC in 15%, 49% and 66% of patients, respectively. Globally, 164 (73%) patients underwent a liver resection at some point of their disease history, and 54 (33%) of them underwent a subsequent locoregional treatment. Age > 70 years, locoregional nodal involvement at diagnosis of colorectal cancer and ≥4 liver metastases were significantly associated with higher risk of ePD while liver resections were associated with reduced risk of ePD. In the multivariable model, number of liver metastases (subdistribution HR, SHR 1.63, 95% CI 1.12 to 2.36; p = 0.01) and liver resections (SHR 0.43, 95% CI 0.29 to 0.63; p = 0.001) were still associated with ePD. Number of liver metastases < 4, no nodal involvement at diagnosis and liver resections were also associated with prolonged ePFS. Conclusions: The identified clinical factors could help physicians in personalising the intensity and aggressiveness of liver-directed treatments in patients with mCRC with initially unresectable LLD.

BACKGROUND The phase III TRIBE and TRIBE2 studies randomized metastatic colorectal cancer patients to first-line FOLFOXIRI/bevacizumab or a doublet (FOLFIRI or FOLFOX)/bevacizumab. The studies demonstrated a significant benefit from the triplet at the price of an increased incidence of chemotherapy-related adverse events (AEs). In both trials, males and females aged between 18 and 70 years with ECOG PS ≤2 and between 71 and 75 years with ECOG PS = 0 were eligible. We investigated the effect of FOLFOXIRI/bevacizumab versus doublets/bevacizumab according to age and gender. PATIENTS AND METHODS Subgroup analyses according to age (

Tumors bearing homologous recombination deficiency are extremely sensitive to DNA double strand breaks induced by several chemotherapeutic agents. ATM gene, encoding a protein involved in DNA damage response, is frequently mutated in colorectal cancer (CRC), but its potential role as predictive and prognostic biomarker has not been fully investigated. We carried out a multicenter effort aimed at defining the prognostic impact of ATM mutational status in metastatic CRC (mCRC) patients. Mutational profiles were obtained by means of next-generation sequencing. Overall, 35 out of 227 samples (15%) carried an ATM mutation. At a median follow-up of 56.6 months, patients with ATM mutated tumors showed a significantly longer median overall survival (OS) versus ATM wild-type ones (64.9 vs 34.8 months; HR, 0.50; 95% CI, 0.29–0.85; P = 0.01). In the multivariable model, ATM mutations confirmed the association with longer OS (HR, 0.57; 95% CI, 0.33–0.98; P = 0.04). The prognostic impact of ATM mutations was independent from TP53 mutational status and primary tumor location. High heterogeneity score for ATM mutations, possibly reflecting the loss of wild-type allele, was associated with excellent prognosis. In conclusion, we showed that ATM mutations are independently associated with longer OS in patients with mCRC.

BRAF mutations occur in 8–12% of metastatic colorectal cancers (mCRC) and more than 95% of them consist in a T>A transversion in exon 15 resulting in an amino acid substitution from valine to glutamic acid (V600E) that is able to increase BRAF kinase activity by approximately 10-fold (1,2).

e15566 Background: Regorafenib is a treatment option for refractory mCRC patients with no validated predictors of benefit. We previously showed that, among several circulating angiogenic factors, low baseline Ang-2 and Tie-2 plasma levels were associated with good prognosis and that the early increase of Ang-2 during the treatment could predict benefit from regorafenib ( Antoniotti et al, J Clin Oncol 36:675-675, 2018). To prospectively validate these retrospective findings, we conducted the REGOLAND study. Methods: Ang-2 and Tie-2 were assessed by ELISA on plasma samples collected at baseline (d1) and after 15 days (d15) of treatment in a cohort of mCRC patients receiving regorafenib, as per indication. To detect a HR for PFS of 0.50 in favour of the early increase (Δd15-d1) of Ang-2 levels, setting two-sided α = 0.05 and β = 0.10, 87 events were required according to Schoenfeld design. Comparisons among concentrations of each marker at d1 and d15 were performed by Wilcoxon test. Median values at baseline were used as cut-off to discriminate patients with low versus high plasma levels and their correlation with outcome was analysed. Results: One hundred patients were included. Median PFS and OS were 2.5 and 6.7 months, respectively. The early increase of Ang-2 at d15 was reported in 42 patients and was associated with longer PFS (median 2.7 vs 2.4 months; HR for PFS: 0.72 [95%CI:0.48-1.08], P = 0.095). As compared to d1, an overall decrease of Tie-2 levels at d15 was observed ( P = 0.007), but it was not associated with clinical outcome. Low levels of Ang-2 at baseline were associated with longer PFS (HR: 0.59 [95%CI:0.39-0.89], P = 0.005) and OS (HR:0.62 [95%CI:0.41-0.94], P = 0.017), while Tie-2 levels were not. In the multivariate model, the association of Ang-2 levels with PFS was confirmed (HR:0.48 [95%CI:0.31-0.76], P = 0.001), but not with OS (HR: 0.80 [95%CI:0.49-1.28], P = 0.351). Conclusions: Ang-2 is a prognostic marker and its early modulation predicts clinical benefit among mCRC patients treated with regorafenib. We hypothesize that Ang-2 levels early increase as a consequence of the successful inhibition of Tie-2 by regorafenib that leads to a compensatory increase of the ligand and correlates with anti-tumour activity.

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.

Background FOLFOXIRI plus bevacizumab is considered a standard option in the upfront treatment of clinically selected patients with metastatic colorectal cancer irrespective of RAS and BRAF molecular status. The randomised MACBETH and VOLFI studies showed that a modified FOLFOXIRI regimen in combination with cetuximab or panitumumab, respectively, achieved high therapeutic activity in RAS and BRAF wild-type patients with an acceptable toxicity profile. Drawing from these considerations, we designed TRIPLETE study aiming at comparing two different chemotherapy backbones (mFOLFOXIRI or mFOLFOX6) in combination with panitumumab in the first-line treatment of patients with RAS and BRAF wild-type metastatic colorectal cancer. Methods This is a prospective, open-label, multicentre phase III trial in which initially unresectable and previously untreated RAS and BRAF wild-type metastatic colorectal cancer patients are randomised to receive a standard treatment with mFOLFOX6 plus panitumumab or an experimental regimen with modified FOLFOXIRI (irinotecan 150 mg/m2, oxaliplatin 85 mg/m2, L-leucovorin 200 mg/m2, 5-fluoruracil 2400 mg/m2 48-hour continuous infusion) plus panitumumab up to 12 cycles, followed by panitumumab plus 5-fluorouracil and L-leucovorin until disease progression. The primary endpoint is overall response rate according to RECIST 1.1 criteria. Discussion The relative benefit of chemotherapy intensification when using an anti-EGFR-based regimen in molecularly selected patients is unknown; TRIPLETE study aims at filling this gap of knowledge. The study is sponsored by the Gruppo Oncologico Nord Ovest Cooperative Group and is currently ongoing at 42 Italian centres. Clinical trial information NCT03231722.

Background Many factors, including histopathologic parameters, seem to influence the prognosis of patients undergoing resection of colorectal cancer liver metastases (CRCLM), although their relative weight is unclear. Histopathologic growth patterns (HGPs) of CRCLM may affect sensitivity to antiangiogenics. We aimed at evaluating differences in histopathologic parameters of response according to the use of bevacizumab or cetuximab as first-line targeted agents, and at exploring the prognostic and predictive role of HGPs. Methods We performed a comprehensive histopathologic characterisation of CRCLM from 159 patients who underwent secondary resection, after receiving triplets FOLFOXIRI (folinic acid, 5-fluorouracil, oxaliplatin, and irinotecan) or COI (capecitabine, oxaliplatin, and irinotecan) plus bevacizumab (N = 103) vs cetuximab (N = 56) in five first-line no-profit clinical trials. Results Both major histopathologic response (tumour regression grade TRG1–2, 32 vs 14%, p = 0.013) and infarct-like necrosis (80 vs 64%, p = 0.035) were significantly higher in the bevacizumab than in the cetuximab group. Achieving major response positively affected relapse-free survival (RFS) (p = 0.012) and overall survival (OS) (p = 0.045), also in multivariable models (RFS, p = 0.008; OS, p = 0.033). In the desmoplastic HGP (N = 28), a higher percentage of major response was reported (57 vs 17% in pushing and 22% in replacement HGP, p

Background FOLFOXIRI plus bevacizumab is considered a standard option in the upfront treatment of clinically selected patients with metastatic colorectal cancer irrespective of RAS and BRAF molecular status. The randomised MACBETH and VOLFI studies showed that a modified FOLFOXIRI regimen in combination with cetuximab or panitumumab, respectively, achieved high therapeutic activity in RAS and BRAF wild-type patients with an acceptable toxicity profile. Drawing from these considerations, we designed TRIPLETE study aiming at comparing two different chemotherapy backbones (mFOLFOXIRI or mFOLFOX6) in combination with panitumumab in the first-line treatment of patients with RAS and BRAF wild-type metastatic colorectal cancer. Methods This is a prospective, open-label, multicentre phase III trial in which initially unresectable and previously untreated RAS and BRAF wild-type metastatic colorectal cancer patients are randomised to receive a standard treatment with mFOLFOX6 plus panitumumab or an experimental regimen with modified FOLFOXIRI (irinotecan 150 mg/m2, oxaliplatin 85 mg/m2, L-leucovorin 200 mg/m2, 5-fluoruracil 2400 mg/m2 48-hour continuous infusion) plus panitumumab up to 12 cycles, followed by panitumumab plus 5-fluorouracil and L-leucovorin until disease progression. The primary endpoint is overall response rate according to RECIST 1.1 criteria. Discussion The relative benefit of chemotherapy intensification when using an anti-EGFR-based regimen in molecularly selected patients is unknown; TRIPLETE study aims at filling this gap of knowledge. The study is sponsored by the Gruppo Oncologico Nord Ovest Cooperative Group and is currently ongoing at 42 Italian centres. Clinical trial information NCT03231722.

Background Refining the selection of metastatic colorectal cancer patients candidates for anti-epidermal growth factor receptor (EGFR) monoclonal antibodies beyond RAS and BRAF testing is a challenge of precision oncology. Several uncommon genomic mechanisms of primary resistance, leading to activation of tyrosine kinase receptors other than EGFR or downstream signalling pathways, have been suggested by preclinical and retrospective studies. Patients and methods We conducted this multicentre, prospective, case-control study to demonstrate the negative predictive impact of a panel of rare genomic alterations [PRESSING (PRimary rESiStance IN RAS and BRAF wild-type metastatic colorectal cancer patients treated with anti-eGfr monoclonal antibodies) panel], including HER2/MET amplifications, ALK/ROS1/NTRK1-3/RET fusions and PIK3CA mutations. Hypothesizing a prevalence of candidate alterations of 15% and 0% in resistant and sensitive RAS and BRAF wild-type patients, respectively, with two-sided α and β errors of 0.05 and 0.20, 47 patients per group were needed. Results Forty-seven patients per group were included. PRESSING panel alterations were significantly more frequent in resistant (24 out of 47, 51.1%) than in sensitive (1 out of 47, 2.1%) patients (P

Background Mutations in PIK3CA, an EGFR downstream effector, and the subsequent activation of AKT pathway plays an important role in colorectal carcinogenesis. Considering the frequent co-occurrence of PIK3CA and RAS mutations, conflicting data exist about its impact on prognosis of mCRC patients (pts) and its predictive role to anti-EGFR therapy. However, PI3K inhibitors have been developed and are currently under investigation in mCRC. Methods Data from mCRC pts treated at Azienda Ospedaliero-Universitaria Pisana from 1 Jan 2005 to 31 Dec 2017, whose tumours had been analysed per clinical practice by MALDI-TOF MassArray were retrieved. Association between PIK3CA mutation and clinico-pathological features was analysed by χ2 test; OS curves were estimated with Kaplan-Meier method and compared by log-rank test. Results Tumours from 90 (17%) out of 542 pts included in this analysis were PIK3CA mutated (mut), most of them in exon 9 (58.9%) or 20 (21.1%). Compared to PIK3CA wild-type (wt) tumours, mut ones were more often RAS mut (P = 0.006), MSI high (P = 0.008), and right-sided (P = 0.0004). Among 53 pts for whom PIK3CA status was available on both primary tumours (PT) and metastasis, the concordance was 92.4%. PIK3CA mutations were not associated with OS (36.4 vs 35.9 mos, HR 1.17, 95%CI 0.85-1.62, p = 0.3), with no difference among those affecting exon 9 and 20 (36.4 vs 27.5 mos, HR 0.77, 95%CI 0.39-1.54, p = 0.44). In RAS/BRAF wt (N 188) and in RAS mut (N 299) subgroup, no difference in terms of OS was found between PIK3CA mut and wt pts (38.1 vs 44.4 mos, HR 1.22, 95%CI 0.60-2.48, p = 0.55 and 27.5 vs 34.4 mos, HR 1.26, 95%CI 0.85-1.86, p = 0.22, respectively), though PIK3CA mut had shorter OS. In BRAF mut subgroup (N 54), PIK3CA mut pts had longer OS compared to PIK3CA wt (not reached vs 14.4 mos, HR 0.37, 95%CI 0.16-0.85, p = 0.09). Among 39 chemorefractory RAS/BRAF wt pts evaluable for response to an anti-EGFR agent, only 2 were exon 9 PIK3CA mut and achieved stable disease. Conclusions PIK3CA mut tumours displayed specific clinico-pathological features and a strong concordance was found between PT and paired metastases. Interestingly, a different impact on prognosis of PIK3CA mutation in RAS/BRAF wt, RAS mut or BRAF mut mCRC pts was observed and deserves validation. Legal entity responsible for the study The authors. Funding Supported by ARCO (Associazione Ricerca e Cure in Oncologia) Foundation. Disclosure All authors have declared no conflicts of interest.

Background Late lines of therapy (LL) offered to cancer patients (pts) are often characterized by scarce or doubtful clinical benefit and literature evidences about their use and their real impact on survival and quality of life are very few. ESMO-MCBS (ESMO Magnitude of Benefit Scale) is a tool that gives an evaluation of the magnitude of clinically meaningful benefit that can be expected from anti-tumour therapies. The aim of our study was to evaluate ESMO-MCBS of the treatments that were offered as a LL to pts in our centre and to perform an evaluation of the clinical assistance they received. Methods We calculated ESMO-MCBS of the therapies that were offered as LL to pts that were treated at our centre and whose death happened in the period from January 1st, 2017 to December 31st, 2018. We also evaluated these pts’rate of unplanned access to emergency room or hospitalizations and their access to supportive care and palliative care service in the last 90 days of their lives. Results 238 pts were included in the analysis. 12 (5.04%) pts received a LL with a high ESMO-MCBS (4 or 5), 16 (6.72%) a LL with an intermediate ESMO-MCBS, 77 (32.35%) a LL with a low ESMO-MCBS (1 or 2), and 133 (55.88%) a LL whose ESMO-MCBS could not be calculated because of lack of data from strong literature evidences (e.g. phase-3 trials) that are required for the scale. 79 pts (33.19%) had at least an unplanned access to emergency room or hospitalization during the last 90 days before death. 117 pts (49.16%) accessed at least once to our supportive and palliative care service in the same timeframe. Conclusions Our study confirmed that patients are often offered a LL whose clinical benefit is little, absent or unevaluable. Merely half of these pts are addressed to supportive/palliative care service whose clinical impact is high in this setting. On the one hand, we then strongly suggest integrating ESMO-MCBS as a clinical tool for the evaluation of possible LL offered to advanced-stage pts in order to prevent them from receiving therapies of poor clinical impact. On the other hand it becomes mandatory to offer these pts a timely access to valuable, more precocious supportive and palliative care, which can positively impact on their quality of life in the last months of their lives. Legal entity responsible for the study The authors. Funding Has not received any funding. Disclosure All authors have declared no conflicts of interest.

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.

3536 Background: FOLFOXIRI/bevacizumab is a valuable upfront option in mCRC based on results of phase III TRIBE and TRIBE2 studies: 1187 pts aged 18–70 years with ECOG performance status (PS) ≤ 2 or between 71–75 years with an ECOG PS of 0 were randomized to receive first-line FOLFOXIRI/bevacizumab or a doublet (FOLFIRI in TRIBE and mFOLFOX6 in TRIBE2)/bevacizumab. Here, we aimed at assessing the effect of the intensification of the upfront chemotherapy (triplet versus doublet) in terms of safety and efficacy in pts aged < 70 versus 70-75. Methods: Subgroup analyses for ORR, PFS, G3/4 overall adverse events (AEs), chemo-related and bevacizumab-related AEs were performed according to baseline age. Results: 182 (15%) out of 1187 pts were 70-75 years old (97 in the FOLFOXIRI/bevacizumab and 85 in the doublets/bevacizumab arms). The benefit provided by the intensification of the upfront chemotherapy was independent of the age subgroup in terms of both ORR (p for interaction = 0.684) and PFS (p for interaction = 0.634). The risk of overall and chemo-related G3/4 AEs was increased with the triplet independently of age (p for interaction = 0.736 and 0.790), while no difference in bevacizumab-related AEs was observed in both subgroups (p for interaction = 0.566). In the overall population, as compared to younger pts, those aged 70-75 were more susceptible to overall G3/4 AEs (70% vs 57%, p = 0.001). In the FOLFOXIRI/bevacizumab arm a higher incidence of G3/4 diarrhea (27% vs 17%, p = 0.016) and febrile neutropenia (16% vs 6% p = 0.001) and a lower incidence of all grade nausea (51% vs 65%, p = 0.009) and vomiting (26% vs 44% p = 0.001) were reported among elderly pts. Conclusions: The activity and efficacy of FOLFOXIRI/bevacizumab are confirmed among selected pts between 70 and 75 years old, with a relative increase in the risk of chemo-related AEs similar to that of younger pts. However, elderly pts are more susceptible to experience AEs independently of the treatment arm. Considering the increased incidence of febrile neutropenia and diarrhea with FOLFOXIRI/bevacizumab, the use of G-CSF as primary prophylaxis or an initial dose reduction of irinotecan and 5-fluorouracil might be considered in this population.

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]

Secondary resection is a chance of cure for a subgroup of metastatic colorectal cancer (mCRC) patients with unresectable liver-limited disease. Medical treatment has a dual goal: to induce tumour shrinkage and to prevent disease relapse. The aims of the present analysis were to assess the efficacy of FOLFOXIRI plus bevacizumab in this setting, and to investigate whether this regimen could revert the poor prognosis of high-risk patients defined by clinical and molecular factors. We performed a pooled analysis of patients with unresectable and liver-limited mCRC, treated with first-line FOLFOXIRI plus bevacizumab in three prospective clinical trials by Gruppo Oncologico del Nord Ovest. 205 (37.9%) patients with liver-limited disease were selected, out of 541 treated patients. Liver metastases were synchronous, ≥4 and bilobar in 90%, 61%, and 79% of cases, respectively. The largest diameter was5 cm in 42% of cases, and ≥6 segments were involved in 25%. Seventy-four patients (36.1%) underwent R0 or R1 resection of metastases. R2 resections were performed in 17 cases (8.3%). Having6 involved segments (p 0.001) and achieving RECIST response (p = 0.019) were associated with higher chances of resection. R0/R1 resected patients had significantly longer median progression-free survival (PFS) (18.1 versus 10.7 months, HR: 0.48 [0.35-0.66], p 0.001) and overall survival (OS) (44.3 versus 24.4 months, HR: 0.32 [0.22-0.48], p 0.001) compared with other patients, both in the univariate and multivariate analyses (PFS p = 0.025; OS p 0.001). The 5-year PFS and OS rate in R0 resected patients were 12% and 43%, respectively. Neither negative baseline characteristics nor high clinical risk scores or RAS/BRAF mutations were associated with poor post-resection outcomes. In conclusion, FOLFOXIRI plus bevacizumab demonstrates efficacy in the conversion setting with considerable long-term outcome results independent of clinical and molecular prognostic factors (NCT00719797, NCT01163396 and NCT02271464).

e15593Background: The high mutational load of dMMR CRCs elicits a considerable endogenous immune anti-tumor response, counterbalanced by immune inhibitory signals. We aimed at describing the immune...

e15511Background: In the last years, availability of active upfront systemic regimens, development of surgical techniques and diffusion of locoregional treatments (LrTx) increased the therapeutic o...

Aim: RECOURSE trial has shown a benefit for trifluridine/tipiracil (also known as TAS-102) over placebo in chemorefractory metastatic colorectal cancer (mCRC) patients. We evaluated efficacy and safety of patients treated with trifluridine/tipiracil in compassionate use. Patients & methods: RETROTAS is a retrospective study designed to evaluate efficacy and safety of trifluridine/tipiracil in mCRC patients previously exposed or not a candidate to all available drugs. Results: A total of 85 mCRC patients were included. Our data showed that 37.6% of patients achieved disease control. Median progression-free survival was 2.3 months; at 16 months follow-up, median overall survival was 9.2 months. Conclusion: This real-life experience confirms the safety and efficacy of trifluridine/tipiracil, resulting as a valid option in chemorefractory mCRC treatment scenario.

636 Background: The histopathological response to pre-operative chemotherapy is associated with clinical outcome in patients (pts) undergoing secondary resection of CRCLM. Three different histopathological growth patterns (HGPs) of CRCLM have been described: desmoplastic (i.e. with a capsule of stroma separating tumor and normal cells), pushing (i.e. with limited infiltration of normal hepatic plates by tumor cells) and replacement (i.e. with abundant infiltration of normal hepatic plates by tumor cells and vessel cooption). Methods: Histopathological parameters of response were evaluated in specimens from 159 pts who underwent secondary resection of CRCLM, after receiving triplet (FOLFOXIRI or COI) plus bev (N = 103) or anti-EGFR (N = 56) in 5 first-line clinical studies (TRIBE, MOMA, MACBETH, COI-B and COI-E). The aims of this analysis were to evaluate the prognostic role of histopathologic response and to investigate the prognostic role of HGPs and their potential different sensitivity to targeted agents. Results: When compared with partial (TRG 3) and no (TRG 4-5) pathologic response (N = 118), major response (TRG 1-2, N = 41) was associated with longer RFS (mRFS: 28.0 versus 11.0 mos, HR = 0.57, 95%CI = 0.39–0.86; p = 0.007) and OS (mOS: unreached versus 42.1 mos, HR = 0.54, 95%CI = 0.31-0.93; p = 0.027). No association of baseline clinical characteristics and RAS and BRAF status with major response was found. Major response was more frequent among pts treated with bev than with anti-EGFRs (OR = 2.83, 95%CI = 1.20–6.65; p = 0.015) and was associated with deepness of response as a continuous variable (HR = 1.02, 95% CI = 1.00–1.04; p = 0.011). In the desmoplastic HGP (N = 28) a higher percentage of major response was reported (57% vs 17% in pushing and 22% in replacement HGP, p < 0.001) and a numerical advantage from anti-EGFR vs bev was evident in terms of both major response and RFS. Conversely, in the pushing HGP (N = 66) a significant benefit from bev vs anti-EGFR in major response and RFS was observed. No difference was described in the replacement HGP (N = 65). Conclusions: The assessment of HGPs may be useful to predict benefit from available targeted agents.

675 Background: Regorafenib is a treatment option for refractory mCRC pts. Considering its limited clinical benefit and the palliative setting, patients’ selection is essential to optimize the cost-effectiveness ratio. We aimed to describe the modulation of selected circulating angiogenic factors by regorafenib and to investigate their correlation with clinical outcome. Methods: IL-8, Ang-2, PDGF, bFGF, Tie-2, sVEGFR2, sVEGFR3, PlGF, VEGF-A, VEGF-B were assessed by ELISA on plasma samples collected at baseline (d1), after 15 days of treatment (d15), at the best RECIST response, at disease progression (PD) in mCRC pts treated with regorafenib, as per indication. Comparisons among concentrations of each marker at different timepoints were performed by Wilcoxon test. Markers showing significant changes were analyzed for correlation with outcome. Results: 105 pts were included. Median PFS and OS were 2.1 and 7.0 months (mos), respectively. As compared to d1, IL-8 and Ang-2 levels increased at PD. An early decrease at d15 was observed for PDGF, Tie-2, sVEGFR2 and sVEGFR3 levels, followed by an increase at PD. Conversely, PlGF levels increased at d15 and then decreased at PD. Baseline levels of Ang-2 and Tie-2 below the median value were associated with longer PFS (HR:0.61 [0.37-0.83] p = 0.006; HR:0.69 [0.43-0.95] p = 0.04, respectively) and OS (HR:0.45 [0.26-0.60] p < 0.0001; HR:0.68 [0.44-0.98] p = 0.04, respectively). With regard to Ang-2, 40 (45%) out of 89 pts with available plasma samples at d15 showed increased levels at d15 as compared to d1. Among them, 21 (53%) achieved disease control, as compared to 14 out of 49 (29%) pts with Ang-2 decreased levels (p = 0.03). Median PFS of pts with increased and decreased Ang-2 levels were 3.1 and 1.8 mos, respectively (HR:0.57 [0.33-0.78] p = 0.004). Conclusions: A dynamic modulation of plasma angiogenic factors occurs during the treatment with regorafenib. Low baseline Ang-2 and Tie-2 levels seem to be associated with good prognosis. The early modulation of Ang-2 levels may predict benefit from regorafenib. These results need validation in independent series.

11508 Background: Almost half of RAS and BRAFwt mCRC patients do not respond to anti-EGFRs. Different molecular alterations suggested as predictors of resistance have not been validated. Methods: We conducted a case-control study to prospectively demonstrate the negative predictive impact of HER-2 amplification or mutations (mut), MET amplification, NTRK/ROS1/ALK/RET rearrangements, and mut activating MAPKs or PI3K/Akt axis. Patients with RAS and BRAFwt mCRC clearly resistant (cases) or clearly sensitive (controls) to anti-EGFRs were selected. Hypothesizing a prevalence of candidate alterations of 0% and 15% among controls and cases, 47 cases and 47 controls were needed to be able to reject the null hypothesis of equally prevalent alterations, with a- and b- error 0.05 and 0.20. Since hypermutated tumors may hardly rely on a single pathway for their growth, we also evaluated the impact of microsatellite instability. Results: 47 cases and 47 controls were included. Primary endpoint was met: mentioned alterations were reported in 20 (42.6%) cases and 1 (2.1%) control (p

12 Background: According to the ESMO guidelines a metastatic spread involving up to 2 or occasionally 3 sites with 5 or sometimes more metastases (mts) is defined as oligometastatic disease (OMD) and the possibility to offer locoregional treatments (LRTs) should be carefully considered. Tumor load and treatment’s objective (cytoreduction vs disease control) are included among factors affecting the choice of the intensity of the upfront chemotherapy (CT). Nevertheless, no data from clinical trials adopting this definition are currently available, so that the prognostic effect of tumor load, the impact of LRTs and the magnitude of benefit from the CT-intensification in OMD remain unclear. Here we assess the effect of FOLFOXIRI/bev compared to doublets (FOLFOX or FOLFIRI)/bev and the impact of LRTs according to tumor load (OMD vs non-OMD) in a pooled analysis of two randomized phase III studies (TRIBE and TRIBE2). Methods: Subgroup analyses for ORR, PFS and OS were performed according to tumor load at baseline. OMD was defined as up to 5 mts, up to 3 mts in one organ, up to 3 affected organs, mts size ≤ 3 cm, absence of ascites and peritoneal, bone and central nervous system mts. Results: Among 1187 patients (pts) enrolled, 1158 were classifiable: 126 as OMD (11%) and 1032 as non-OMD (89%). Pts with OMD had longer PFS (14.3 vs 10.5 months (mos); p < 0.01) and OS (44.3 vs 24.0 mos; p < 0.01) compared with those with non-OMD. These results were confirmed in multivariable models (p < 0.01). Also among pts who underwent LRTs with curative intent during first line (N = 202), those with OMD at baseline (N = 35) reported longer OS than those with non-OMD (59.6 vs 50.6 mos; p = 0.04). The benefit provided by FOLFOXIRI/bev compared to doublets/bev was confirmed in the OMD subgroup with no interaction effect between treatment arm and tumor load in terms of ORR, PFS and OS (p for interaction = 0.10, 0.58 and 0.23, respectively). Conclusions: OMD is confirmed as a positive prognostic factor and is associated with a higher magnitude of long-term benefit from LRTs than non-OMD. The positive impact of the intensification of the upfront CT is independent of tumor load.