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Chemotherapy followed by margin-negative resection (R0) is the treatment of choice for patients with localized pancreatic ductal adenocarcinoma (PDAC). Neoadjuvant multiagent chemotherapy (MAC) or MAC then radiotherapy (RT) may optimize surgical candidacy. The purpose of this study was to compare pathologic outcomes of MAC followed by conventionally fractionated radiotherapy (CRT) versus stereotactic body radiotherapy (SBRT) for patients with resected PDAC.Patients diagnosed with nonmetastatic PDAC between 2012 and 2017 and who received preoperative MAC or MAC+RT were identified in the National Cancer Database. Variables associated with R0 and overall survival were identified with logistic regression and Cox analysis (P0.05).A total of 5273 patients were identified (MAC: 3900, MAC+CRT: 955, MAC+SBRT: 418). The median RT dose/fraction (fx) in the MAC+CRT and MAC+SBRT cohorts was 50.4 Gy/28 fx and 33 Gy/5 fx. Patients receiving MAC+CRT versus MAC+SBRT had similar rates of ypT3-T4 disease (54% vs. 58%, P=0.187), R0 (87% vs. 84%, P=0.168), and pathologic complete response (pathologic complete response; 6% vs. 4%, P=0.052), however, MAC+CRT was associated with less regional lymphatic disease (ypN+: 28% vs. 41%, P0.001). The median overall survival of patients receiving MAC+CRT versus MAC+SBRT was 24.6 versus 29.5 months (P=0.045).For patients with resected PDAC, MAC+CRT, and MAC+SBRT had similar rates of R0 and pathologic complete response, although MAC+CRT was associated with lower ypN+. Prospective evaluation of neoadjuvant RT regimens with attention to radiation therapy design is warranted.

To investigate if a simplified image based scoring system assessing treatment response after neoadjuvant therapy (NAT) can predict survival in patients with pancreatic ductal adenocarcinoma (PDAC) who achieved subsequent R0 resection. Retrospective analysis of 57 PDAC patients (male = 29, 51%) with mean age of 64 at diagnosis (range 42–79) who received NAT and R0 resection. Post-NAT overall, arterial and venous imaging response was characterized as improved, similar, or worse by 2 readers independently followed by consensus review. Kaplan–Meier Analysis was performed to compare overall survival (OS) with post-NAT overall imaging response. A Multivariable Cox proportional hazards analysis was performed to evaluate the association of the following variables with OS: overall, arterial and venous radiology response, clinical staging, postoperative CA19-9, and patient age. At study conclusion, 30/57 patients were deceased (53%), 26/57 (46%) alive, and 1 patient unknown. Post-NAT, 39/57 (68.4%) had overall improved disease and 18/57 (31.6%) had similar disease. The median OS was 55.7 months (95% CI 33.4–not reached, NR) for those with improved disease vs. 53.9 months (95% CI 14.3–NR) with similar disease (p = 0.859) after NAT. Among all clinical parameters, only post-operative CA 19-9 level was associated with OS (p = 0.002) and PFS (p = 0.005), respectively. Pancreatic cancer patients who underwent R0 resection showed no difference in survival when comparing those with similar vs improved disease on post-NAT imaging.

Background and aimsDNA repair deficiency is a common feature of cancer. Homologous recombination (HR) and nucleotide excision repair (NER) are the two most frequently disabled DNA repair pathways in solid tumors. HR deficient breast, ovarian, pancreatic and prostate cancers respond well to platinum chemotherapy and PARP inhibitors. However, the frequency of DNA repair pathway deficiency in gastric and esophageal adenocarcinoma (GEA) still lacks diagnostic and functional validation. Furthermore, whether DNA repair deficient GEA have enhanced responsiveness to platinum chemotherapy and sensitivity to PARP inhibitors is not well characterized.MethodsUsing whole exome and genome sequencing data, we measured various HR deficiency-associated mutational signatures in patient specimen of gastric, esophageal and colorectal cancer specimens and gastric cancer cell lines. Gold-standard immunofluorescence assays were used to confirm HR and NER deficiency in cancer cell lines. The relationship between PARP inhibitor treatment and tumor response was evaluated in patients with gastric cancer. Drug sensitivity was determined using standard in vitro cell culture assays. Single-cell RNA-sequencing was performed to evaluate gastric cancer response to commonly used chemotherapeutics.ResultsWe found that a significant subset of GEA, but very few colorectal tumors, show evidence of HR deficiency by mutational signature analysis (HRD score). Gastric cancer cell lines with high HRD mutational signature scores demonstrated functional HR deficiency by RAD51 assay and increased sensitivity to platinum and PARP inhibitors. There was a positive association between HRD scores and tumor response in patients with gastric cancer treated with a PARP inhibitor on a clinical trial. A gastric cancer cell line with strong sensitivity to cisplatin showed HR proficiency but exhibited NER deficiency by DDB2 proteo-probe assay. Single-cell RNA-sequencing revealed that, in addition to inducing general apoptosis, cisplatin treatment triggered ferroptosis in a NER-deficient gastric cancer, which may explain the outlier sensitivity.ConclusionA subset of upper gastrointestinal tumors have genomic features of HR and NER deficiency and therefore may be more likely to benefit from platinum chemotherapy and PARP inhibition.

Introduction: Many patients do not benefit from immunotherapies targeting immune checkpoints such as PD(L)-1 due to a variety of resistance mechanisms. The AhR pathway is downstream of the Trp-IDO/TDO-Kyn axis. High levels of immune-suppressive AhR-activating ligands, such as kynurenine derived from IDO1/TDO2-expressing tumors, have been implicated as a potential resistance mechanism and are associated with poor responses to PD-1 therapies. Compared with inhibition of IDO1/TDO2 alone, direct AhR inhibition can block the activation of this transcription factor and may better counteract immune suppression. BAY2416964 is a novel, oral AhR inhibitor currently in a Phase I clinical trial in patients with solid tumors. Preclinically, BAY2416964 can block the activation of AhR by kynurenine and relieve its immune-suppressive effects, thereby restoring anti-tumor T-cell activity, reducing the level of inhibitory myeloid-derived suppressor cells and regulatory T cells, and improving the effectiveness of PD-1 blockade. We have analyzed PK and biomarker data from the ongoing monotherapy dose-escalation study to explore a potential optimal dose and schedule for effective AhR inhibition. Methods: PK data were intensely sampled from patients in 10 different groups with different dosing regimens (once and twice daily) and various food-intake scenarios. AhR downstream target gene expression after ex vivo kynurenic acid stimulation of patients’ peripheral blood mononuclear cells (PBMCs) was assessed. A population PK (popPK) model was developed and calibrated to characterize the PK of BAY2416964 across treatment groups. This model accounts for the non-linear relationship between dose and bioavailability as well as the effect of food intake. Results: The preliminary popPK model identified a non-linear relationship between the BAY2416964 dose and its (relative) bioavailability which was dependent on the respective food condition. The popPK model was able to describe the clinical BAY2416964 plasma exposures from all dose groups, including the effect of food intake. Ex vivo analysis of PBMCs showed inhibition of kynurenic acid-induced AhR downstream gene expression (such as CYP1A1, CYP1B1), suggesting effective in vivo target engagement in the doses tested. Conclusion: This modeling-based PK analysis along with target engagement in peripheral blood informed the posology to be tested in the dose-expansion part of the ongoing clinical trial. Citation Format: Kyriakos Papadopoulos, Michael Cecchini, Juanita S. Lopez, Dirk Jäger, Ki Young Chung, Michael Platten, Florian Prinz, Yuko Ishii, David Schaer, Ilona Gutcher, Gabriele Leder, Radost Pencheva, Thomas Wagener, Christian Scheerans, Carsten Zieschang, Andrea Wagner, Spyros Stamatelos, Ecaterina Dumbrava. Preliminary analysis of pharmacokinetic (PK) and target engagement biomarkers from a first in human phase 1 study of immunomodulatory aryl hydrocarbon receptor (AhR) inhibitor BAY2416964 [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 2 (Clinical Trials and Late-Breaking Research); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(8_Suppl):Abstract nr CT276.

Introduction: ATRi and PARPi combinations kill tumor cells via synergistic modulation of complementary DDR pathways but clinical utility is limited by overlapping toxicities. A genome-wide CRISPR-Cas9 screen identified DDR alterations that sensitize tumors to the ATRi camonsertib (cam) plus PARPi. Based on preclinical models, tolerability and efficacy of cam plus PARPi given intermittently at low doses in pts with solid tumors with DDR alterations, including BRCA-mutated PARPi-resistant cancers, was evaluated. Methods: Pts (≥ 18 yrs) with relapsed/refractory (r/r) solid tumors with DDR alterations were treated with cam plus talazoparib (tala), niraparib (nira), or olaparib (ola) in 2 phase I trials (NCT04497116, NCT04972110). An adaptive BOIN design was used to optimize dose/schedule. Endpoints were safety, recommended phase II dose (RP2D), pharmacokinetics (PK), response (RECIST v1.1 [confirmed/unconfirmed], CA 125, or PSA), clinical benefit rate (CBR; RECIST/tumor marker response or treatment duration ≥ 16 wk), and ctDNA molecular response rate (MRR; best reduction in mean variant allele frequency [mVAF] ≥ 50%). Results: As of Nov 2022, 99 pts were enrolled (61 with ≥ 3 prior lines of therapy, 36 PARPi-pretreated); 43, 27, 29 pts in tala, nira, and ola combinations, respectively. Tumors included ovarian (n=20), prostate (n=13), breast (n=17), bile duct (n=3); most common genotypes were ATM (n=26), BRCA1 (n=19), and BRCA2 (n=33). Grade 3+ toxicities included reversible myelosuppression (neutropenia, anemia, and thrombocytopenia in 35%, 28%, and 14% of pts overall; 33%, 16%, and 11% at preliminary RP2Ds), fatigue (3%), and alkaline phosphatase increase (2%). Two pts discontinued treatment due to drug-related toxicity. Forty pts remain on therapy, up to 63 wks. Preliminary RP2Ds: cam 80 mg QD (d 5-7) + tala 0.25 mg QD, 1 wk on/1 wk off; cam 80 mg QD + nira 100 mg QD, 2 d on/5 d off; cam 50 mg QD + ola 100 mg BID, 3 d on/4 d off. As of abstract submission, response rate was 13% in 85 evaluable pts; CBR was 49%. Responders included pts with ovarian (n=6), bile duct (n=2), and breast, pancreatic, and carcinoma of unknown primary (n=1 each) cancers harboring alterations in BRCA1/2 (n=9), IDH1 (n=1), and ATM (n=1). Of 30 evaluable PARPi-pretreated pts, response rate was 23% and CBR was 52%. MRR was 64% (14/22 evaluable); change in mVAF correlated with a change in target lesion size (r=0.63, P=0.001). PK of each drug in the combination was consistent with respective monotherapy PK. Conclusion: Combination of cam plus PARPi at low doses on intermittent schedules was generally well-tolerated with clinical activity in DDR-aberrant tumors, including those pretreated with PARPi. RP2D optimization and translational correlative studies are ongoing. Citation Format: Timothy A. Yap, Siddhartha Yadav, Benjamin Herzberg, Benedito A. Carneiro, Elisa Fontana, Martin Højgaard, Michael J. Pishvaian, Ruth Plummer, Theresa L. Werner, Vaibhav Sahai, Stephanie Lheureux, Elizabeth K. Lee, Niharika B. Mettu, Gregory M. Cote, Joseph D. Schonhoft, Victoria Rimkunas, Ian M. Silverman, Marisa Wainszelbaum, Gerson Peltz, Adrian J. Fretland, Kezhen Fei, Danielle Ulanet, Insil Kim, Maria Koehler, Ezra Rosen, Michael Cecchini. Safety and efficacy of three PARP inhibitors (PARPi) combined with the ataxia telangiectasia- and Rad3-related kinase inhibitor (ATRi) camonsertib in patients (pts) with solid tumors harboring DNA damage response (DDR) alterations [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 2 (Clinical Trials and Late-Breaking Research); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(8_Suppl):Abstract nr CT018.

Highlights • Complete resection is a potentially curative treatment for pancreatic cancer. • This report studies neoadjuvant chemotherapy with or without radiation. • The addition of radiation was associated with improved complete resection rates. • The addition of radiation was associated with improved pathologic down staging., Purpose Margin-negative (R0) resection is the only potentially curative treatment for patients with pancreatic ductal adenocarcinoma (PDAC). Pre-operative multi-agent chemotherapy alone (MAC) or MAC followed by pre-operative radiotherapy (MAC + RT) may be used to improve resectability and potentially survival. However, the optimal pre-operative regimen is unknown. Methods Patients with non-metastatic PDAC from 2006 to 2016 who received pre-operative MAC or MAC + RT before oncologic resection were identified in the National Cancer Database. Univariable and multivariable (MVA) associates with R0 resection were identified with logistic regression, and survival was analyzed secondarily with the Kaplan Meier method and Cox regression analysis. Results 4,599 patients were identified (MAC: 3,109, MAC + RT: 1,490). Compared to those receiving MAC, patients receiving MAC + RT were more likely to have cT3-4 disease (76% vs 64%, p

Background: This study sought to assess microsatellite and KRAS status, prevalence, and impact on outcome in stage IV colorectal cancer (CRC). Materials and Methods: The 2010 to 2016 US National Cancer Database was queried for adult patients with stage IV CRC. Prevalence of microsatellite status (microsatellite instability–high [MSI-H] or microsatellite stable [MSS]) and KRAS status (KRAS mutation or wild-type) of the primary CRC was assessed. Overall survival (OS) was evaluated using multivariable Cox proportional hazards models in patients with complete data on both microsatellite and KRAS status and information on follow-up. Results: Information on microsatellite and KRAS status was available for 10,844 and 25,712 patients, respectively, and OS data were available for 5,904 patients. The overall prevalence of MSI-H status and KRAS mutation was 3.1% and 42.4%, respectively. Prevalence of MSI-H ranged between 1.6% (rectosigmoid junction) and 5.2% (transverse colon), and between 34.7% (sigmoid colon) and 58.2% (cecum) for KRAS mutation. MSI-H rates were highest in East North Central US states (4.1%), and KRAS mutation rates were highest in West South Central US states (44.1%). Multivariable analyses revealed longer OS for patients with KRAS wild-type versus mutation status (hazard ratio [HR], 0.91; 95% CI, 0.85–0.97; P=.004), those with MSS versus MSI-H status (HR, 0.75; 95% CI, 0.62–0.9; P=.003), and those with left-sided versus right-sided CRC (multivariable HR, 0.65; 95% CI, 0.6–0.7; P<.001). The effect of KRAS mutation further varied with CRC site and microsatellite status (P=.002 for interaction). Conclusions: Depending on the primary site and US geography, stage IV CRC shows distinct mutational behavior. KRAS mutation, MSI-H, and primary CRC sidedness independently affect OS and interact with distinct prognostic profiles. Generically classifying adenocarcinomas at different sites as CRC might deprecate this diversity.

Background Pyoderma gangrenosum (PG) is a rare neutrophilic dermatosis characterized by painful and ulcerating lesions on the skin. It rarely involves the face and is often difficult to diagnose. There are few cases reported in the literature of PG involving the face. Aim To share our experience with 5 patients in whom the final diagnosis was PG involving the face, and to review the literature. Methods We report a series of 5 patients with a final diagnosis of PG involving the face and reviewed relevant literature. We searched through PubMed and EMBASE using keywords such as “face” and “pyoderma gangrenosum,” “blastomycosis-like pyoderma gangrenosum, vegetative pyoderma gangrenosum and granulomatous pyoderma gangrenosum.” Results We report 5 patients (4 females) with pyoderma gangrenosum involving the face. All 5 had a final diagnosis of superficial granulomatous PG. All cases presented with nonhealing facial ulcer most commonly on cheeks and a common histopathology of mixed inflammatory infiltrates, multinucleated giant cells, and plasma cells with some granulomatous inflammation. Conclusions PG can involve the face, and all 5 of our patients had the superficial granulomatous as the most common form.

Expert consensus on the potential benefits of early cancer detection does not exist for most cancer types. We convened 10 practicing oncologists using a RAND/UCLA modified Delphi panel to evaluate which of 20 solid tumors, representing >40 American Joint Committee on Cancer (AJCC)-identified cancer types and 80% of total cancer incidence, would receive potential clinical benefits from early detection. Pre-meeting, experts estimated how long cancers take to progress and rated the current curability and benefit (improvement in curability) of an annual hypothetical multi-cancer screening blood test. Post-meeting, experts rerated all questions. Cancers had varying estimates of the potential benefit of early cancer detection depending on estimates of their curability and progression by stage. Cancers rated as progressing quickly and being curable in earlier stages (stomach, esophagus, lung, urothelial tract, melanoma, ovary, sarcoma, bladder, cervix, breast, colon/rectum, kidney, uterus, anus, head and neck) were estimated to be most likely to benefit from a hypothetical screening blood test. Cancer types rated as progressing quickly but having comparatively lower cure rates in earlier stages (liver/intrahepatic bile duct, gallbladder, pancreas) were estimated to have medium likelihood of benefit from a hypothetical screening blood test. Cancer types rated as progressing more slowly and having higher curability regardless of stage (prostate, thyroid) were estimated to have limited likelihood of benefit from a hypothetical screening blood test. The panel concluded most solid tumors have a likelihood of benefit from early detection. Even among difficult-to-treat cancers (e.g., pancreas, liver/intrahepatic bile duct, gallbladder), early-stage detection was believed to be beneficial. Based on the panel consensus, broad coverage of cancers by screening blood tests would deliver the greatest potential benefits to patients.

Background TAS-102, a novel antimetabolite, is approved for treatment of refractory metastatic colorectal cancer (CRC). This study sought to determine whether the addition of TAS-102 to oxaliplatin (TAS-OX) was safe and effective in metastatic CRC previously treated with oxaliplatin. Methods This investigator-initiated, open-label, single-arm phase 1b study enrolled patients with metastatic CRC previously treated with 5-fluorouracil, irinotecan, and oxaliplatin. In dose escalation, TAS-102 was given at 3 dose levels: 25, 30, and 35 mg/m2 twice daily on day 1 to day 5 with 85 mg/m2 oxaliplatin on day 1 in 14-day cycles. The primary endpoint of dose escalation was the recommended dose for expansion, and in dose expansion, the primary endpoint was overall response rate (ORR) according to the Response Evaluation Criteria in Solid Tumors (RECIST, version 1.1). Results Forty-one patients were treated with TAS-OX. No dose-limiting toxicities were observed in the 11 patients treated in escalation. The recommended dose for expansion was 35 mg/m2 TAS-102 twice daily on day 1 to day 5 in combination with 85 mg/m2 oxaliplatin on day 1 in 14-day cycles. In the intention-to-treat population, the ORR was 2.4% (95% CI, 0%-12.9%) with 1 of 41 patients having a partial response, although 12 (29%) had tumor shrinkage. The median progression-free survival was 2.7 months (95% CI, 2.4-4.8 months) and median overall survival was 6.8 months (95% CI, 5.7-10 months). Conclusions TAS-OX is safe with no unexpected toxicities at standard doses of each agent. The combination did not result in a clinically meaningful ORR, although progression-free survival and overall survival were encouraging in this heavily pretreated population. Lay summary For metastatic colorectal cancer, the treatment combination of TAS-102 and oxaliplatin was found to be well-tolerated and revealed no unexpected side effects. Twelve of 41 patients had reductions in the size of their tumor, and the study treatment delayed the time to tumor growth as opposed to what would be expected.

BACKGROUND: Mismatch repair (MMR) deficiency is the hallmark of tumours from Lynch syndrome (LS), sporadic MLH1 hypermethylated and Lynch-like syndrome (LLS), but there is a lack of understanding of the variability in their mutational profiles based on clinical phenotypes. The aim of this study was to perform a molecular characterisation to identify novel features that can impact tumour behaviour and clinical management. METHODS: We tested 105 MMR-deficient colorectal cancer tumours (25 LS, 35 LLS and 45 sporadic) for global exome microsatellite instability, cancer mutational signatures, mutational spectrum and neoepitope load. RESULTS: Fifty-three percent of tumours showed high contribution of MMR-deficient mutational signatures, high level of global exome microsatellite instability, loss of MLH1/PMS2 protein expression and included sporadic tumours. Thirty-one percent of tumours showed weaker features of MMR deficiency, 62% lost MSH2/MSH6 expression and included 60% of LS and 44% of LLS tumours. Remarkably, 9% of all tumours lacked global exome microsatellite instability. Lastly, HLA-B07:02 could be triggering the neoantigen presentation in tumours that show the strongest contribution of MMR-deficient tumours. CONCLUSIONS: Next-generation sequencing approaches allow for a granular molecular characterisation of MMR-deficient tumours, which can be essential to properly diagnose and treat patients with these tumours in the setting of personalised medicine.

29 Background: Brain metastases (BM) are rare in colorectal cancer (CRC) with 1-3% of patients developing BM over their lifetime. There are no screening recommendations for BM in patients with CRC and most are diagnosed after a patient develops symptoms. Identifying the clinical characteristics for patients with CRC and BM may aid clinicians to consider BM early in symptom onset and potentially screen appropriate patients. Methods: We performed a retrospective chart review of patients >18 years diagnosed with CRC and BM at Yale New Haven Hospital from 1/2012-9/2021. Clinical characteristics were analyzed by descriptive statistics, time intervals were compared using the Mann-Whitney test, and survival analysis was done using the Kaplan-Meier method. Results: We identified 93 patients with CRC and BM. Median age at diagnosis was 56 years, 55% were male, 75% of patients had a left sided primary tumor and 47% were rectal primary. At initial diagnosis, 38% and 39% were stage III and IV respectively. RAS/RAF mutations were present in 45% of patients and all were mismatch repair proficient. The median time from CRC diagnosis to BM was 3.81 years (95% CI 3.09, 4.41) and median time from metastatic CRC to BM was 2.21 years (95% CI 1.48, 2.75). Median overall survival after developing BM was 0.49 years (95% CI 0.24, 0.70). Patients with RAS/RAF mutations had a decreased median time from CRC diagnosis to BM of 3.33 years (95% CI 2.69, 4.37) compared to RAS/RAF wildtype at 5.09 years (95% CI 4.44, 7.97) (p 0.0028). Median time to BM from CRC diagnosis was also decreased in females (p 0.01). The location of primary tumor did not significantly decrease time to BM. Prior to BM diagnosis, 76% of patients had lung metastasis. 84% of patients received treatment for BM while 14% had no BM treatment and 2% were unknown. For treatment 50% had Gamma Knife Radiosurgery, 22% underwent surgical excision +/- adjuvant radiation, and 12% underwent whole brain radiotherapy. After BM treatment, 43% of patients received additional chemotherapy. Conclusions: Although BM in CRC is uncommon, early diagnosis in those at risk is critical given the urgent nature of BM. Patients with CRC that develop BM frequently have tumors that originate in the left side of the colon and preexisting lung metastasis. In patients with CRC and BM, the majority develop BM > 3 years after initial CRC diagnosis, and BM onset is significantly shorter in females and patients with tumors harboring a RAS/RAF mutation. After BM diagnosis and treatment, less than half of patients are able to receive subsequent therapy, and median survival is < 6 months. [Table: see text]

115 Background: BI 905711 is a tetravalent bispecific antibody that cross-links TRAILR2 with CDH17. This cross-linking drives CDH17-dependent TRAILR2 oligomerization, leading to caspase activation and eventual apoptosis, inhibiting tumor growth in preclinical models of GI cancer. Methods: This Phase Ia/b study of BI 905711 in patients (pts) with advanced GI cancers (NCT04137289) aimed to determine the maximum tolerated dose (MTD) based on the proportion of pts with dose-limiting toxicities (DLT) and explore preliminary antitumor activity. In Phase Ia, pts received BI 905711 every 14 days. One pt with colorectal cancer (CRC) was enrolled at each of the 2 lowest dose levels (0.02/0.06 mg/kg) and 4 pts with CRC were enrolled at each subsequent level (0.2/0.6/1.2/2.4/3.6/4.8 mg/kg). Up to 4 pts with non-CRC GI cancers were included at the dose level below the CRC cohort. Dose escalation was guided by a Bayesian logistic regression model. Results: As of 01 August 2022, 48 pts (CRC: n = 26; non-CRC: n = 22, including 13 with pancreatic ductal adenocarcinoma [PDAC]) had received BI 905711 (dose range 0.02–4.8 mg/kg); pts had a median age of 61 years (range 27–78) and had received a median of 3 (range 1–11) prior lines of treatment. No DLTs were observed and the MTD was not reached. 41 pts had AEs (grade [G] 3–5: 14 pts; serious: 13 pts). 17 pts had treatment-related AEs (TRAEs); 4 TRAEs were G3: AST increased (2 pts), fatigue and ALT increased (1 pt each). 1 pt had serious TRAEs: G2 decreased appetite and G3 fatigue. 2 pts had G1/2 infusion-related reactions that resolved and did not prevent resumption of treatment. PD biomarker modulation on the level of plasma caspase-3/7 activity was most common at 0.6 mg/kg (4/7 pts) or 1.2 mg/kg (2/6 pts). 13 pts achieved stable disease (SD) and 8 pts were progression-free for ≥4 months (PFS4). In pts with CRC, 6 pts achieved SD and 3 had PFS4. Among non-CRC pts, 7 pts achieved SD (PDAC: n = 6) and 5 had PFS4 (PDAC: n = 4). Median duration of treatment was 30.5 days (range 15–246) overall and 71 days (range 15–211) in the 0.6 mg/kg group (n = 8, predicted therapeutic dose; of whom 3 pts had PFS4: CRC: n = 1/4 [all CDH17+]; non-CRC: n = 2/4). Conclusions: In heavily pretreated pts, BI 905711 was associated with a tolerable safety profile and early signs of disease control. BI 905711 will be further assessed in Phase Ib in 4 dose groups: 0.6/1.2/2.4 mg/kg every 14 days, and 0.6 mg/kg weekly. Clinical trial information: NCT04137289 .

Background Treatment for metastatic colorectal cancer patients beyond the second line remains challenging, highlighting the need for early phase trials of combination therapies for patients who had disease progression during or following two prior lines of therapy. Leveraging hybrid control design in these trials may preserve the benefits of randomization while strengthening evidence by integrating historical trial data. Few examples have been established to assess the applicability of such design in supporting early phase metastatic colorectal cancer trials. Methods MORPHEUS-CRC is an umbrella, multicenter, open-label, phase Ib/II, randomized, controlled trial (NCT03555149), with active experimental arms ongoing. Patients enrolled were assigned to a control arm (regorafenib, 15 patients randomized and 13 analysed) or multiple experimental arms for immunotherapy-based treatment combinations. One experimental arm (atezolizumab + isatuximab, 15 patients randomized and analysed) was completed and included in the hybrid-control study, where the hybrid-control arm was constructed by integrating data from the IMblaze370 phase 3 trial (NCT02788279). To estimate treatment efficacy, Cox and logistic regression models were used in a frequentist framework with standardized mortality ratio weighting or in a Bayesian framework with commensurate priors. The primary endpoint is objective response rate, while disease control rate, progression-free survival, and overall survival were the outcomes assessed in the hybrid-control study. Results The experimental arm showed no efficacy signal, yet a well-tolerated safety profile in the MORPHEUS-CRC trial. Treatment effects estimated in hybrid control design were comparable to those in the MORPHEUS-CRC trial using either frequentist or Bayesian models. Conclusions Hybrid control provides comparable treatment-effect estimates with generally improved precision, and thus can be of value to inform early-phase clinical development in metastatic colorectal cancer.

BACKGROUND: FOLFIRINOX (FFX) and gemcitabine plus nab-paclitaxel (GN) are established first line therapies for metastatic pancreatic cancer (MPC). There are, however, no randomized controlled trials comparing FFX and GN in the first line setting and real-world data on their comparative effectiveness is limited. We aimed to evaluate the outcomes of patients with MPC who were treated with first line FFX and GN and to further characterize dose modifications, discontinuation rates due to treatment toxicity, and rates of hospitalizations while on treatment. METHODS: We manually abstracted data from the electronic medical records (EMR) system at Yale Smilow Hospital and Smilow Cancer Hospital Care Centers for patients with MPC treated with at least one cycle of first line FFX or GN from January 2011 to April 2019. Patients who received prior neoadjuvant or adjuvant FFX or GN and adjuvant gemcitabine less than 6 months prior to metastatic recurrence were excluded. The median time to treatment discontinuation (TTD) and overall survival (OS) were determined using Kaplan-Meier method. RESULTS: We identified 363 patients for analysis; 269 (74%) patients were treated with FFX and 94 (26%) with GN. Median TTD was 4.8 (IQR, 2.3–8.0) months in the FFX group compared to 3.4 (IQR, 1.3–5.7) months in the GN group (P=0.0037). Median OS was 11.3 (95% CI: 10.7–12.9) months in the FFX group and 7.0 (95% CI: 6.0–8.7) months in the GN group (P

Pyoderma gangrenosum (PG) is a rare neutrophilic dermatosis characterized by painful and ulcerating lesions on the skin. It rarely involves the face and is often difficult to diagnose. There are few cases reported in the literature of PG involving the face.To share our experience with 5 patients in whom the final diagnosis was PG involving the face, and to review the literature.We report a series of 5 patients with a final diagnosis of PG involving the face and reviewed relevant literature. We searched through PubMed andEMBASE using keywords such as "face" and "pyoderma gangrenosum," "blastomycosis-like pyoderma gangrenosum, vegetative pyoderma gangrenosum and granulomatous pyoderma gangrenosum."We report 5 patients (4 females) with pyoderma gangrenosum involving the face. All 5 had a final diagnosis of superficial granulomatous PG. All cases presented with nonhealing facial ulcer most commonly on cheeks and a common histopathology of mixed inflammatory infiltrates, multinucleated giant cells, and plasma cells with some granulomatous inflammation.PG can involve the face, and all 5 of our patients had the superficial granulomatous as the most common form.

Background: Ramucirumab is a monoclonal antibody that binds to the vascular endothelial growth factor receptor 2, increasing hypoxia in the tumor microenvironment. In advanced gastric cancer, single agent ramucirumab is well tolerated and improves overall survival (OS) compared to placebo although it is largely cytostatic with a response rate ≤3%. Preclinical in vitro and in vivo experiments reveal that hypoxia induces homologous recombination deficiency (HRD) in tumors, which may be exploited by the addition of inhibitors of poly (ADP-ribose) polymerase (PARPi). We thus designed NCI10066 for metastatic gastric cancer with the hypothesis that ramucirumab would sensitize tumors to the PARPi olaparib. Methods: NCI 10066 (NCT03008278) was a phase 1/2, multicenter, open-label clinical trial sponsored by the Cancer Therapy Evaluation Program. Eligible patients had histologically confirmed metastatic gastric or GEJ adenocarcinoma with measurable disease refractory to ≥ 1 prior therapy that did not contain ramucirumab. Patients were treated with escalating doses of olaparib with ramucirumab 8 mg/kg every 2 weeks in a 3+3 design. Dose escalation evaluated two dose levels: olaparib 200 mg twice daily with ramucirumab 8 mg/kg every 2 weeks (dose level 1) and olaparib 300 mg twice daily with ramucirumab 8 mg/kg every 2 weeks (dose level 2). The primary objective of dose escalation was to assess safety and measure dose limiting toxicities (DLT) to determine the recommended phase 2 dose (RP2D). The primary objective in phase 2 was to evaluate clinical activity at the RP2D in a 40-patient expansion cohort. Results: From 2/8/18 - 9/17/21, 51 patients were enrolled at 10 centers throughout the Experimental Therapeutics Clinical Trials Network and 28/51 (55%) patients had ≥2 prior lines of therapy. In dose escalation 3 patients were treated at dose level 1 and 8 at dose level 2. No DLTs were observed at dose level 1 and at dose level 2 there was 1 DLT (fatigue) in 6 evaluable patients. The RP2D was determined to be olaparib 300 mg twice daily and ramucirumab 8 mg/kg every 2 weeks. Forty patients were treated in dose expansion at the RP2D. Of 46 patients evaluable for a response there were 5/46 (11%) partial responses (PR) and the disease control rate (PR/SD) was 29/46 (63%) at 6 weeks. The median progression free survival (PFS) was 2.8 months (95% CI 2.3 - 4.2) and the median OS was 7.3 months (95% CI 5.6 - 13.0). Grade ≥ 3 treatment related adverse events were seen in 13 (25%) of patients and there were no treatment related deaths. Conclusions: The combination of olaparib and ramucirumab is well tolerated with a RP2D of olaparib 300 mg twice daily and ramucirumab 8 mg/kg every 2 weeks. The ORR, PFS, and OS exceed the historical control with ramucirumab monotherapy, suggesting that the combination is clinically active. Biomarkers are critical to defining patient subsets more likely to benefit from the combination and HRD biomarker analysis is ongoing. Citation Format: Michael Cecchini, Joseph Chao, Yu Shyr, James Cleary, Nataliya Uboha, May Cho, Anthony Shields, Shubham Pant, Laura Goff, Kristin Spencer, Edward Kim, Chih-Yuan Hsu, Stacey Stein, Jaykumar Thumar, Jeremy Kortmansky, John Kunstman, Patricia LoRusso, Percy Ivy, Jill Lacy. A phase 1/2 study of olaparib in combination with ramucirumab in metastatic gastric and gastroesophageal junction adenocarcinoma (GEJ) [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr CT170.

3535 Background: Approximately 20% of colorectal cancer (CRC) has an activating mutation in the PIK3CA oncogene. PIK3CA codes for the catalytic subunit of phosphoinositide 3-kinase alpha (PI3Kα), which ultimately activates the AKT and mammalian target of rapamycin (mTOR) pathway. The PI3Kα inhibitor alpelisib has been approved for breast cancer where a single PIK3CA activating mutation is sufficient for response. However, two activating mutations (multi-hit) in the PIK3CA allele substantially increases PI3Kα signaling compared to single hot spot mutations and results in exceptional response to PI3Kα inhibition. We aimed to identify the prevalence of PIK3CA multi-hit mutations in CRC to identify patients potentially susceptible to PI3K inhibitors. Methods: Tissue-based comprehensive genomic profiling (CGP) was performed in a Clinical Laboratory Improvement Amendments (CLIA)-certified, CAP (College of American Pathologists)-accredited laboratory (Foundation Medicine Inc., Cambridge, MA, USA) on all-comers during the course of routine clinical care from 2013-2021. Approval was obtained from the Western Institutional Review Board (Protocol No. 20152817). Hybrid capture was carried out for at least 324 cancer-related genes, including PIK3CA. Results: We identified 48,836 patients with advanced CRC who underwent Foundation Medicine testing and 846 (1.7%) patients with multi-hit PIK3CA mutations. Additional clinical and molecular data was available for 41,154 of these patients of which 710 (1.7%) had multi-hit PIK3CA and 7627 (19%) had any deleterious PIK3CA mutation . The local colon tumor was used for sequencing in 70% of cases and a separate site in 30% of cases. Patients with PIK3CA multi-hit mutations were 53% male with a median age of 60 (interquartile range 50-70). The microsatellite status was available for 697 of 710 patients with multi-hit PIK3CA and 123/697 (18%) were microsatellite instability-high. The Table outlines the genes with cooccurring mutations of >10% prevalence for multi-hit PIK3CA CRC, including the clinically relevant mutations in KRAS (65%) and BRAF (13%). The four most common PIK3CA variants were H1047R (9.8%), E545K (9.2%), E542K (9.0%) and R88Q (7.1%). The most common variant pair was E542K with E545K in 4.7% of multi-hit cases. Conclusions: Double-hit mutations in PIK3CA are seen in 1.7% of advanced CRC patients and may represent a subset of patients that may have enhanced sensitivity to PI3K inhibitors. Given the high prevalence of CRC in the United States and worldwide this represents a clinically meaningful prevalence of multi-hit PIK3CA. Future investigation on the clinical utility of PI3K inhibitors may be warranted in multi-hit PIK3CA CRC.[Table: see text]

Background Expert knowledge is often shared among multidisciplinary academic teams at tumor boards (TBs) across the country, but these conversations exist in silos and do not reach the wider oncology community. Objective Using an oncologist-only question and answer (Q&A) website, we sought to document expert insights from TBs at National Cancer Institute–designated Comprehensive Cancer Centers (NCI-CCCs) to provide educational benefits to the oncology community. Methods We designed a process with the NCI-CCCs to document and share discussions from the TBs focused on areas of practice variation on theMednet, an interactive Q&A website of over 13,000 US oncologists. The faculty translated the TB discussions into concise, non–case-based Q&As on theMednet. Answers were peer reviewed and disseminated in email newsletters to registered oncologists. Reach and engagement were measured. Following each Q&A, a survey question asked how the TB Q&As impacted the readers’ practice. Results A total of 23 breast, thoracic, gastrointestinal, and genitourinary programs from 16 NCI-CCC sites participated. Between December 2016 and July 2021, the faculty highlighted 368 questions from their TBs. Q&As were viewed 147,661 times by 7381 oncologists at 3515 institutions from all 50 states. A total of 277 (75%) Q&As were viewed every month. Of the 1063 responses to a survey question on how the Q&A affected clinicians’ practices, 646 (61%) reported that it confirmed their current practice, 163 (20%) indicated that a Q&A would change their future practice, and 214 (15%) reported learning something new. Conclusions Through an online Q&A platform, academics at the NCI-CCCs share knowledge outside the walls of academia with oncologists across the United States. Access to up-to-date expert knowledge can reassure clinicians’ practices, significantly impact patient care in community practices, and be a source of new knowledge and education.

Background Randomized controlled trials (RCTs) are the gold standard for evidence-based practice, but their development and implementation is resource intensive. We aimed to describe modern RCTs in gastrointestinal (GI) cancer and identify predictors of successful accrual and publication. Materials and Methods ClinicalTrials.gov was queried for phase III GI cancer RCTs opened between 2010 and 2019 and divided into two cohorts: past and recruiting. Past trials were analyzed for predictors of successful accrual and the subset with ≥3 years follow-up were analyzed for predictors of publication. Univariate and multivariable (MVA) logistic regression were used to identify covariates associated with complete accrual and publication status. Results A total of 533 GI RCTs were opened from 2010 to 2019, 244 of which are still recruiting. In the “past” trials cohort (235/533) MVA, Asian continent of enrollment was a predictor for successful accrual, whereas trials with prolonged enrollment (duration longer than median of 960 days) trended to failed accrual. Predictors for publication on MVA included international enrollment and accrual completion. Sponsorship was not associated with accrual or publication. Notably, 33% of past trials remain unpublished, and 60% of trials that were closed early remain unpublished. Conclusion Accrual rate and the primary continent of enrollment drive both trial completion and publication in GI oncology. Accrual must be streamlined to enhance the impact of RCTs on clinical management. A large portion of trials remain unpublished, underscoring the need to encourage dissemination of all trials to, at a minimum, inform future trial design. Implications for Practice Two-thirds of gastrointestinal (GI) oncology phase III randomized controlled trials successfully accrue; however, one third of these trials are unpublished and more than half of trials that close early are unpublished. The strongest predictors for publication are successful accrual and international collaborations. Initiatives to optimize the trial enrollment process need to be explored to maximize the potential for trials to engender progress in clinical practice. Moreover, this study identified a significant publication bias in the realm of GI oncology, and the field should promote reporting of all trials in order to better inform future trial questions and design.

Despite a decreasing incidence in the USA, gastric cancer is highly prevalent worldwide. Furthermore, gastric cancer remains highly lethal with median survival of less than 1 year for metastatic disease. The backbone of therapy against metastatic gastric cancer remains cytotoxic chemotherapy, but recent advances in the molecular understanding of gastric cancer have renewed hope within that targeted agents can be leveraged to improve survival and reduce toxicity. For example, in patients with human epidermal growth factor-2 (HER2)-positive gastric cancer, the addition of trastuzumab to frontline chemotherapy improves survival. In the second line, oncologists can now administer a vascular endothelial growth factor (VEGF) receptor inhibitor, ramucirumab, as a single agent or in combination with chemotherapy, and the immune checkpoint inhibitor pembrolizumab is approved in multiple settings dependent on the Programmed Death Ligand 1 (PD-L1) status. For patients with metastatic disease, our approach to standard of care in the first-line setting is a 5FU/platinum doublet with trastuzumab for HER2-positive tumors. In the second-line setting, most patients receive ramucirumab + paclitaxel, but those that are MSI high receive pembrolizumab. For squamous cell carcinoma of the esophagus with high PD-L1 status (combined positive score (CPS) ≥ 10), we recommend pembrolizumab in the second line. While for PD-L1 ≥ 1% gastroesophageal adenocarcinoma, we do not recommend pembrolizumab before the third-line setting, although this may change in the near future for CPS ≥ 10. The future landscape for targeted therapy in gastric cancer is promising. Numerous clinical trials evaluating the combination immune therapy with molecularly targeted agents are generating much excitement. Moreover, genomic data from The Cancer Center Genome (TCGA) and Asian Cancer Research Group (ACRG) classifications is being used to identify molecular subtypes to enable future clinical trials to include biomarker-enriched patient populations.

OBJECTIVES In the 5-fluorouracil, leucovorin, irinotecan, and oxaliplatin (FOLFIRINOX) era, the benefit of surgery versus definitive radiation for borderline resectable (BR) and locally advanced (LA) unresectable pancreatic ductal adenocarcinoma (PDAC) is not well defined. Our primary objective was to identify the survival impact of surgery for BR and LA unresectable PDAC treated with induction FOLFIRINOX. METHODS We performed a single-center retrospective review of BR and LA PDAC treated with FOLFIRINOX from 2010 to 2018. The overall survival of surgery and consolidative radiotherapy was estimated in the Kaplan-Meier method and compared via the log-rank test. Subgroup analyses were conducted for BR and LA patients. RESULTS We identified 101 BR and LA PDAC patients treated with induction FOLFIRINOX (41 surgeries and 60 consolidative radiotherapies). Surgery patients were 68.3% (28/41) BR and 31.7% (13/41) LA, whereas consolidative radiotherapy patients were 30% (18/60) BR and 70% (42/60) LA. The R0 resection rate was 100%, and 46.3% (19/41) received preoperative radiation. Median overall survival of surgery versus consolidative radiotherapy was 42.3 versus 19.6 months, respectively (P < 0.001). On multivariate analysis, surgery associated with improved survival. CONCLUSIONS Surgery after induction FOLFIRINOX is feasible and has a clinically meaningful survival benefit in BR and LA PDAC.

Interventional oncology (IO) and oncoimmunology (OI) are fields that have significantly evolved during the last two decades and are providing new opportunities to conquer cancer with a safe and effective treatment profile. Novel IO treatments have the potential to complement OI and sensitize “cold” tumors to immunostimulatory therapies with the ultimate aim of improving patient outcomes. In this manuscript, we provide an overview of the current knowledge of the immune system in cancer, the potential for IO to modulate the immune system, and how IO and OI may synergize.

136 Background: O6-methylguanine DNA methyltransferase (MGMT) is the principal repair mechanism of DNA damage created by alkylating agents. Approximately 40% of colorectal cancers (CRC) exhibit MGMT promoter hypermethylation, expected to result in gene silencing. The role of MGMT as a biomarker is poorly understood, and quantitative measurement of MGMT protein has not been performed in CRC. We hypothesized that altered tumor MGMT would affect DNA damage response, modulate adaptive anti-tumor immune responses, and influence survival in CRC. Methods: We used multiplexed quantitative immunofluorescence (QIF) to study 4 clinically annotated retrospective patient cohorts treated from 2000 to 2017 at Yale, consisting of 400 formalin-fixed paraffin-embedded CRC cases represented in tissue microarray format. These included paired tumors and adjacent non-tumor colonic mucosa (n = 112 pairs in Cohort 1), paired primary CRC and lymph node metastases (n = 31 pairs in Cohort 2), and 2 cohorts with primary stage I-IV tumors (n = 250 in Cohort 3; n = 150 in Cohort 4). We established a QIF panel for simultaneous, localized measurement of DAPI (all cells), cytokeratin (CK; tumor epithelial cells), MGMT, γH2AX (DNA damage response), and CD8. The measurement of fluorescent signals in CK-positive tumor cells or CK-negative stromal cells was achieved using co-localization strategies and the AQUA QIF platform. Results: We identified lower MGMT protein levels in CRC cells than in non-tumor colonic epithelium (p < 0.0001), and in lymph node metastases compared to paired primary CRC tumors (p = 0.0411). Using the visual detection threshold, tumor selective MGMT protein downregulation was identified in 20% of cases in Cohorts 3 and 4. Microsatellite instability-high (MSI-H) cases showed decreased tumoral MGMT protein compared to microsatellite stable (MSS) cases (p = 0.002). In Cohorts 3 and 4, low tumoral MGMT was consistently associated with increased CD8+ tumor infiltrating lymphocytes (p = 0.0472; p = 0.0002). The association between MGMT and γH2AX was inconsistent. The association between MGMT and CD8 was significant only in MSS cases (p = 0.0001) but not in MSI-H cases (p = 0.0979), supporting that the effect is not driven by MSI-H status. Tumor-selective MGMT downregulation evidenced by a low tumor-to-stroma ratio was associated with improved progression-free survival and overall survival in both Cohorts 3 and 4, but statistical significance was only seen in Cohort 3. Conclusions: MGMT protein downregulation occurs in 20% of CRCs and is associated with increased adaptive anti-tumor immune responses, mismatch repair (MMR) deficiency and better prognosis. MGMT deficiency may alter DNA repair in tumor cells and mediate the accumulation of antigenic mutations or neopeptides, independent from MMR status. Our results support a biomarker role of MGMT protein and suggest a role for immunotherapy combinations in MGMT deficient tumors.

TPS375 Background: In normal conditions, Claudin (CLDN)18.2 is a tight junction protein with expression strictly confined to differentiated epithelial cells in gastric mucosa. CLDN18.2 has been found to be upregulated, and involved in tumor development and progression in a variety of tumor types such as gastric, pancreatic, and bile duct cancer (BTC). The biological characteristics of CLDN18.2 suggest it is an ideal therapeutic target for cancer drug development. IMAB362 is the first anti-CLDN18.2 monoclonal antibody (mAb) of high potency to have been tested in humans and it revealed clinical efficacy in gastric cancer in a phase II study. TST001, a humanized IgG1 mAb, binds to a distinct epitope of CLDN18.2 with higher affinity and mediates CLDN18.2 expressing cancer cell death through antibody-dependent cellular cytotoxicity (ADCC) in comparison with IMAB362; Furthermore, TST001 is produced using an optimized glycoengineering process to increase affinity to FcR. The enhanced binding to CLDN18.2 on tumor cells and FcR on NK cells results in more efficient engagement of the tumor cells with NK cells and antibody mediated cellular cytotoxicity. In preclinical xenograft studies, TST001 displayed potent anti-tumor activities in the tumor models with medium to high level of CLDN18.2 expression and synergy anti-cancer effect with checkpoint inhibitor. A mAb specific for CLDN18.2 was also developed as an IHC based biomarker for patient enrollment in the clinical trials. Methods: This is an open-label, multi-center, phase I clinical trial to evaluate the safety, maximum tolerated dose (MTD), pharmacokinetics (PK) profile and preliminary anti-cancer effect of TST001 in patients with locally advanced or metastatic solid tumors. (NCT04396821) The study consists of two parts: Part A is a 3+3 dose escalation design with sequential dose cohorts of 1, 3, 6, 10mg/kg in Q2W and Q3W schedules. Based on the emerging safety data, higher doses may be proposed for testing. About 27-54 patients will be enrolled. Dose expansion (Part B) will utilize doses of TST001 based on the emerging data from Part A. In Part B, up to 20 patients with CLDN18.2 overexpression per tumor specific cohort will be enrolled to 3 cohorts: A: TST001 single agent in gastric/gastroesophageal junction (G/GEJ) cancer; B: TST001 + nivolumab in G/GEJ cancer; C: TST001 single agent in pancreatic cancer or BTC. All patients in Part B will be selected by CLDN18.2 expression by central lab testing. The safety, anti-tumor activity, and PK will be further assessed in Part B. Enrolment began in July 2020 in the USA and is ongoing in multiple sites. As of 20 September, 2021, 23 subjects were dosed in Part A and the dose of 10mg/kg is being tested. Another phase I study of TST001 single agent and in combination with chemotherapy in patients with metastatic solid tumor is also ongoing in China (NCT04495296).

TPS222 Background: Activation of the tumor necrosis factor-related apoptosis-inducing ligand receptor 2 (TRAILR2) induces apoptosis via caspase activation. Targeting TRAILR2 is an attractive therapeutic strategy, but some early TRAILR2 agonists were associated with severe hepatotoxicity. Cadherin 17 (CDH17), a membrane protein highly expressed in GI cancers, is not expressed in normal hepatocytes so using CDH17 as a liver-sparing anchor may avoid hepatotoxicity. BI 905711 is a tetravalent bispecific antibody that cross-links TRAILR2 with CDH17 to induce CDH17-dependent TRAILR2 oligomerisation. In preclinical assays, BI 905711 demonstrated a potency shift of ̃1000 fold versus the 1st-generation TRAILR2 agonist lexatumumab. BI 905711 induced apoptosis in CDH17-positive tumor cells in vitro, impaired tumor growth in pt-derived colorectal cancer (CRC) xenografts, and no hepatotoxicity was observed. Methods: This phase Ia/Ib study (NCT04137289) aims to determine the safety, maximum tolerated dose (MTD), pharmacokinetics (PK), pharmacodynamics, and preliminary efficacy of BI 905711 in pts with advanced, refractory GI cancers. Up to 140 adult pts with histologically confirmed, advanced unresectable/metastatic colorectal, gastric, esophageal or pancreatic adenocarcinoma, cholangiocarcinoma, or gallbladder or small intestine carcinoma, who have progressed on standard-of-care therapies, will be enrolled. In phase Ia, pts will receive intravenous BI 905711 at escalating doses (range 0.02–4.8 mg/kg) every 14 days, until disease progression or unacceptable toxicities. Dose escalation will be guided by a Bayesian logistic regression model with overdose control based on dose-limiting toxicities (DLTs) in the first 28 days. In phase Ia, a minimum number of CRC pts will be enrolled to each cohort: ≥1 CRC pt at each of the 2 lowest dose levels (0.02/0.06 mg/kg) and 4 pts at each subsequent dose level (0.2/0.6/1.2/2.4/3.6/4.8 mg/kg). In parallel to dose escalation in CRC pts, up to 4 pts with non-CRC GI cancers will be included at the dose level below that of the CRC cohort. If an objective response (OR) per RECIST v1.1 is observed in CRC or non-CRC GI pts at a safe dose level, up to 10 additional pts with the same tumor type will be recruited at that dose level. In phase Ib, CRC pts will be randomized into up to 4 dose cohorts (as determined in phase Ia; n=20 each) to define the recommended phase II dose. The primary endpoints are determination of the MTD based on the proportion of pts with DLTs (phase Ia) and OR rate based on RECIST v1.1 (phase Ib). Secondary endpoints include PK parameters and OR in pts with measurable disease (phase Ia), and disease control, tumor shrinkage, duration of response, and progression-free survival (phase Ib). Trial enrollment is ongoing, with 33 pts enrolled to date. Clinical trial information: NCT04137289.

Purpose/objective(s) Following presentation of the CALGB 80803 trial, which demonstrated notably high pathologic complete response (pCR) rates with induction FOLFOX followed by chemoradiotherapy (CRT), our institution more routinely incorporated induction chemotherapy (IC) into the management of LA-EC patients. However, improvements in progression-free (PFS) or overall survival (OS) with this regimen compared to pre-operative CRT alone have not yet been shown. We hypothesized IC-CRT would lead to an improvement in OS and PFS when compared to CRT. Materials/methods Patients with operable LA-EC were eligible for analysis if they received CRT between 2013-2019. The cohort was stratified into two groups, IC-CRT vs. CRT. The Kaplan-Meier method was used to estimate OS and PFS. The cumulative incidences of local recurrence (LR), locoregional recurrence (LRR), and distant metastasis (DM) were reported. The impact of treatment group on pathologic response and surgical outcomes were assessed by Chi-square. Results 95 patients were included for analysis (IC-CRT n = 58; CRT n = 37). Baseline characteristics included median Karnofsky Performance Status 80, median weight loss 5% (IQR 0-9%), with the majority being adenocarcinoma histology (81%), T3-T4 (60%), N+ (79%), located in the distal esophagus or gastroesophageal junction (89%). Patients receiving IC-CRT were more likely to have been treated after 2016 (64% vs 38%, P = 0.021). IC was most commonly FOLFOX (74%) for a median of 3 (IQR 1-3) cycles. CRT was delivered to a median dose of 50 Gy in 25-28 fractions. Surgery was attempted in 60% and 68% of the IC-CRT and CRT cohorts, respectively. Median follow-up was 26 months. ICRT and CRT were associated with similar 2-year OS (66% [95% CI 51-78%] vs 70% [95% CI 52-83%]) and PFS (47% [95% CI 33-59%] vs 48% [95% CI 30-63%]). In the adenocarcinoma subset (n = 77), 2-year OS was 69% (95% CI 52-81%) in the IC-CRT cohort vs 61% (95% CI 40-77%) with CRT. 2-year PFS was 46% (95% CI 31-60%) and 38% (95% CI 20-56%), respectively. IC-CRT was not associated with an OS or PFS benefit among any patient subgroup. Recurrence rates were similar between the cohorts (47%) and first recurrence was most commonly DM (61% IC-CRT vs 65% CRT). Patients receiving IC-CRT compared to CRT had numeric but not statistically significant improvement in pCR (45% vs 29%, P = 0.24) and N-stage regression (72% vs 58%, P = 0.28). There was no difference in the rate of R0 resection, hospitalization, surgical complications, or treatment-related death with use of IC-CRT. Conclusion IC-CRT was not associated with improved OS or PFS in this small and perhaps underpowered cohort study. Further investigations are needed to explore the impact of IC-CRT on quality of life, symptom burden, and to see if meaningful trends develop with time.

Background: The release of ATP from dying cancer cells in response to platinum-based chemotherapy increases immunosuppressive extracellular adenosine, which can bind and activate the A2a and A2b receptors on immune cells, diminishing the effectiveness of the anti-tumor immune response. Concomitant dual adenosine receptor blockade may therefore enhance the therapeutic efficacy of some chemotherapeutic agents. Etrumadenant (etruma, AB928) is the first clinical-stage small-molecule, selective dual antagonist of A2aR and A2bR for which combination data with mFOLFOX-6 in mCRC were previously presented1,2. Here we present updated results for safety in all patients (pts) and efficacy in 3L+ pts. Methods: ARC-3 (NCT03720678) was a phase 1/1b, multicenter, open-label study to evaluate etruma + mFOLFOX-6 in pts with mCRC. Eligible pts had histologically confirmed mCRC with ≥1 measurable lesion. Pts received 75 mg (phase 1 only) or 150 mg etruma orally once daily (QD) + mFOLFOX-6. The primary objective was to assess the safety of the combination; secondary objectives included evaluation of clinical activity. Results: As of 20Nov2020, 44 pts were enrolled and received etruma (75mg: n=4; 150mg: n=40) + mFOLFOX-6. Etruma-related AEs were reported in 34 pts and were mostly Grade 1 or 2; those reported in >30% of pts were fatigue and nausea. One pt had an etruma-related Grade 3 acute kidney injury and there were no Grade 4-5 etruma-related SAEs. There were 22 efficacy-evaluable 3L+ subjects, all of which had received prior FOLFOX and/or FOLFIRI. In this subgroup, the ORR was 9.1% and the median PFS and OS were 3.9 and 15.7 mos respectively. Conclusions: Updated results confirm etruma + mFOLFOX-6 was well tolerated in pts with mCRC without significant additive toxicity and was associated with disease control in heavily pretreated pts. Based on these encouraging data, a platform study (ARC-9) has been initiated to further explore this and other combinations in mCRC pts. References 1. Cecchini M, et.al. AACR Annual Meeting 2020, Abstract# 99532. Udyavar A, et.al. SITC Annual Meeting 2020, Abstract# 338 Citation Format: Michael Cecchini, Cheng Quah, Shiyao Liu, Rachel Woloski, Akshata Udyavar, Marios Giannakis. ARC-3: Updated results of etrumadenant (AB928) + modified FOLFOX-6 (mFOLFOX-6) in metastatic colorectal cancer (mCRC) patients [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr CT129.

The prognosis of metastatic pancreatic cancer remains poor despite recent advances in treatment with multidrug chemotherapy regimens. Use of immune checkpoint inhibitors and molecular targeted therapies has so far been disappointing. This report describes a patient with chemotherapy-refractory metastatic pancreatic ductal adenocarcinoma (PDAC) whose tumor was characterized by an activating mutation in exon 19 of the epidermal growth factor receptor (EGFR). He experienced response to erlotinib for 10 months, and then developed disease progression in association with emergence of the T790M mutation. Activating EGFR mutations in cancers other than lung are uncommon, but when present may predict response to EGFR tyrosine kinase inhibitors (TKIs). Development of the T790M mutation in this case suggests that EGFR-targeted TKIs may follow similar patterns of resistance regardless of tumor type. Although actionable mutations are detected infrequently in PDAC, this case illustrates the potential benefit of offering genomic analysis to all patients with advanced disease.

Background: Induction FOLFIRINOX is increasingly used for borderline resectable (BR) and locally advanced (LA) unresectable pancreatic ductal adenocarcinoma (PDAC), but the benefit of surgery versus consolidative radiation in the FOLFIRINOX era is not well defined. Single institution experiences have included FOLFIRINOX with gemcitabine-based chemotherapy, lack a uniform comparator group to surgery, or are limited to surgical patients after FOLFIRINOX. No prospective clinical trials have assessed surgery versus radiation. Therefore, our primary objective was to identify the long-term survival impact of surgery versus radiation for BR and LA unresectable PDAC treated with induction FOLFIRINOX. Methods: We performed a single center retrospective review of BR and LA PDAC treated with FOLFIRINOX from 2010 - 2018. Patients were divided into two cohorts based on receipt of surgery versus consolidative radiotherapy. Findings: We identified 101 BR and LA PDAC patients treated with induction FOLFIRINOX; 40 underwent surgery and 61 received consolidative radiotherapy. The surgery group was 28/40 (70%) BR and 12/40 (30%) LA, while consolidative radiotherapy was 18/61 (30%) BR and 43/61 (70%) LA. The R0 resection rate was 100% for surgery and 18/40 (45%) received radiation prior to surgery. Median overall survival (OS) for surgery was 42·3 months (95% CI 24·6 - not reached) compared to a median OS of 19·6 months (95% CI 16·3 - 24·6) with consolidative radiotherapy(p = 0·0001). On multivariate analysis, surgery was associated with improved OS (HR 0·35, 95% CI 0·17 - 0·71, p=0·004). Interpretation: Surgery after induction FOLFIRINOX is feasible and has a clinically meaningful survival benefit in BR and LA PDAC compared to induction FOLFIRINOX followed by consolidative radiotherapy. Funding Statement: This research was not supported by any funding. Declaration of Interests: The authors declare no conflicts of interest relevant to this manuscript. Ethics Approval Statement: This study was approved by the Yale University institutional review board.

e18584 Background: Cancer progression rates following diagnosis are readily measured. However, the progression rate of cancer during the preclinical sojourn time is generally unobserved. Understanding the duration of preclinical stages (“dwell time”) would allow clinicians to better identify appropriate screening intervals for cancer. We therefore elicited estimates of progression rate during the preclinical sojourn time for a wide variety of malignancies from a panel of clinical experts. Methods: We used a validated consensus methodology (RAND/UCLA modified Delphi panel method) to elicit per-stage dwell time estimates for 20 solid cancers and lymphoma from experts. Eleven experienced oncologists (general and subspecialists) from community and academic centers reviewed literature on the natural history of disease and estimated in number of years (

2624 Background: KY1044, is a fully human IgG1 anti ICOS antibody designed to stimulate Teffs and to deplete ICOS high Tregs in the tumor microenvironment. Methods: Patients with advanced/metastatic malignancies received escalating doses of KY1044 as a single agent and in combination with atezolizumab 1200 mg by IV infusion every 3 weeks until disease progression or unacceptable toxicity. Dose escalation was guided by a modified toxicity probability interval design. The primary objective was to determine safety, tolerability, and maximum tolerated dose. Cohorts that were tolerated were later enriched with more subjects. AEs were classified according to CTCAE v5 and efficacy measures performed according to RECIST v1.1 every 8 weeks for the first 16 weeks and then every 12 weeks. Results: As of 16-Dec-2020, a total of 103 patients have been enrolled in the study (38 patients as monotherapy in 6 cohorts at doses ranging from 0.8 to 240 mg and 65 in combination with atezolizumab in 5 cohorts at doses 0.8 – 80 mg). 63% and 55% of patients received ≥4 prior anti-cancer therapies in the single agent and combination cohorts, respectively. All cohorts were completed without DLTs during the first 21 days of treatment. In the KY1044 single agent cohorts, 47.4% of patients experienced treatment-related AEs (TRAEs), all were grades 1 or 2. In the combination cohorts, TRAEs were observed in 58% of patients. Most of the TRAEs were grade 1 or 2 apart from 8 TRAEs that were ≥grade 3 occurring in 43 weeks (range 45 to 66 weeks). Conclusions: KY1044 is well tolerated as single agent and in combination with atezolizumab. Objective responses have been observed in this phase 1 part of the study. The phase 1 expansion and phase 2 part of the study is ongoing. Clinical trial information: NCT03829501.

TPS150 Background: ATP release from dying cancer cells in response to platinum-based chemotherapy increases extracellular immunosuppressive adenosine, which binds and activates the A2a and A2b receptors on immune cells. Adenosine-mediated signaling impairs activation, proliferation, and cytotoxic activity of effector T cells, resulting in inhibition of antitumor activity. Concomitant adenosine receptor blockade may therefore enhance the therapeutic efficacy of chemo/immunotherapy regimens. Etrumadenant (AB928), the first clinical-stage, small-molecule, dual adenosine receptor antagonist, is highly potent, pharmacodynamically active, and has been well tolerated in dose escalation studies as monotherapy or combined with chemo/immunotherapy. Recently, results were reported for the ARC-3 phase 1/1b study of etrumadenant + modified 5-fluorouracil + oxaliplatin (mFOLFOX-6) in patients (pts) with mCRC. In this study, etrumadenant + mFOLFOX-6 was well tolerated without significant additive toxicity. Disease control was observed in patients with RAS/BRAF mutated mCRC, as well as 3L+ disease previously treated with FOLFOX and/or FOLFIRI (PR and/or SD >4 mo). Due to deep responses in 1L-3L+ pts, 6 pts had the opportunity to pursue surgery and radiotherapy with curative intent. The encouraging results from ARC-3 warrant further evaluation of etrumadenant-based combination therapy for mCRC. Methods: ARC-9 is a phase 1b/2, multicohort, open-label, randomized platform study designed to evaluate safety and clinical activity of etrumadenant (150 mg orally once daily [QD]) in combination with standard-of-care (SOC) regimens or novel therapeutics in pts with mCRC (Table). Cohort eligibility is based on prior anticancer treatment history. Pts enrolled in Cohorts A and B will be randomized (2:1) into the experimental vs SOC arms. Cohort C consists of a single arm to allow inclusion of novel agents as they become available with built in early stopping rules for futility. Pts who progress on the SOC arm of Cohort A can enroll in Cohort B; pts who progress on the SOC arm of Cohort B can crossover to the experimental arm. Primary endpoints across cohorts are shown in Table. Safety monitoring will occur throughout the trial, disease assessments will occur every 8 weeks, and correlative study pre- and on-treatment biopsies will be performed. [Table: see text]

82 Background: The MORPHEUS platform consists of multiple, global, open-label, randomized Phase Ib/II trials designed to identify early efficacy signals and safety of treatment (tx) combinations across tumor types. Isatuximab (isa; anti-CD38) targets CD38 receptors expressed on immunosuppressive cells in the tumor microenvironment. We hypothesized atezolizumab (atezo; anti–PD-L1) + isa would induce an anti-tumor response beyond that of regorafenib (rego), a multi-kinase inhibitor, in patients (pts) with tx-refractory metastatic colorectal cancer (mCRC). Methods: This randomized Phase Ib/II trial (NCT03555149) enrolled pts with microsatellite stable/mismatched repair proficient mCRC who had received ≤ 2 prior tx lines (fluoropyrimidine-, oxaliplatin- or irinotecan-containing chemotherapy plus a biologic agent). Pts received atezo (1200 mg intravenously [IV] every 3 weeks [q3w]) + isa (10 mg/kg IV q3w) or control tx with rego (160 mg orally days 1–21; dose escalation to 160 mg during Cycle 1 allowed per institutional guidelines). The primary endpoint was objective response rate (ORR; investigator-assessed RECIST 1.1); secondary endpoints included progression-free survival (PFS), overall survival (OS), disease control rate (DCR) and safety. Results: Data cutoff date was March 3, 2020. Fifteen pts received atezo + isa and 13 pts received rego. Fourteen atezo + isa pts (93.3%) and 11 control arm pts (84.6%) had received 2 prior lines of tx; 9 atezo + isa pts (60.0%) and 9 control pts (69.2%) had liver metastases at enrollment. No responses were seen in either arm; 3 pts receiving atezo + isa (20.0%) and 8 control pts (61.5%) had stable disease as their best response. DCR (response and/or stable disease ≥ 12 weeks) was 6.7% with atezo + isa and 15.4% with control. One pt treated with atezo + isa beyond progression had prolonged disease stabilization. Median PFS was 1.4 mo (95% CI: 1.4, 1.8) with atezo + isa and 2.8 mo (95% CI: 1.6, 3.1) in the control arm; median OS was 5.1 mo (95% CI: 3.1, 7.8) with atezo + isa and 10.2 mo (95% CI: 4.8, not reached) with control. Tx-related adverse events (AEs, Grade 1-4) occurred in 13 atezo + isa pts (86.7%), and 12 control pts (92.3%). The most common tx-related AEs with atezo + isa were infusion-related reaction (73.3%), nausea (26.7%) and fatigue (20.0%). No Grade 5 AEs occurred in the atezo + isa arm, 1 (7.7%) was reported in the control arm (sepsis, considered unrelated to study tx). No atezo + isa pts and 1 control-arm pt (7.7%) withdrew from treatment due to a tx-related AE. Biomarker analyses did not identify any significant trends related to efficacy. Conclusions: In this trial, superior efficacy of atezo + isa vs rego was not shown. However, the atezo + isa combination was well tolerated, with a manageable safety profile. Clinical trial information: NCT03555149.

462 Background: To evaluate epidemiology, treatment and outcomes of stage 4 gastrointestinal stromal tumors (GIST). Methods: The 2010-2016 United States National Cancer Database was queried for adult patients diagnosed with invasive GIST (ICD code 8936) at AJCC stage 4, without prior malignant disease. Overall survival (OS) was evaluated using Cox proportional hazards regression, accounting for potential confounders in multivariable models. Results: A total of 1,578 stage 4 GIST were included (13.3% of all GIST) with a male:female ratio of 1.38:1. The most common cancer site was the stomach (55.4%) and small intestine (40% of stage 4 GIST). At diagnosis, median age was 62 years and median tumor diameter 10 cm. Distant organ metastases were reported in 58.7%, the most frequent being hepatic (n = 801, 50.8% of stage 4 GIST). The majority of stage 4 GIST patients received systemic therapy (78.6%), either alone (35.4%) or combined surgery+systemic therapy (43.3%). Systemic therapy was administered neoadjuvant in 6.9%, adjuvant in 32%, and neoadjuvant+adjuvant in 5.1% of surgically resected patients. Another n = 204 patients (12.9% of all stage 4 GIST) were treated with surgical resection alone. GIST overall survival rates were 88%, 77%, 67% and 51% at 1, 2, 3, and 5 years, respectively. On multivariable Cox proportional hazard models, primary GIST treatment independently affected OS: compared to combined surgery+systemic therapy, OS was shorter for patients receiving systemic therapy alone (HR = 2.77 (95% CI: 2.12-3.61, p < 0.001)) and no treatment (HR = 4.2 (95% CI: 2.75-6.43, p < 0.001)). No significant OS difference was evident comparing surgery+systemic therapy and surgery alone (HR = 1.23 (95% CI: 0.88-1.72, p = 0.227)). In subgroup analyses of patients undergoing surgical resection, no statistically significant OS difference was evident comparing neoadjuvant, adjuvant and combined neoadjuvant+adjuvant systemic therapy on multivariable analyses. Treatment at non-academic vs. academic centers was associated with shorter OS (multivariable HR = 1.36 (95% CI: 1.1-1.69, p = 0.005)). Further independent OS predictors were male sex (vs. female HR = 1.28 (95% CI: 1.03-1.59, p = 0.023)), older age, higher comorbidities, higher cancer grade, and larger cancer diameter. Conclusions: Stage 4 GIST is a rare gastrointestinal malignancy that most commonly manifests in the stomach and small intestine in male patients, with frequent hepatic metastases and excellent 5-year OS rates of up to 51%. Combined surgery+systemic therapy demonstrates best outcomes, although surgical resection alone might yield comparable results in selected patients.

Purpose: Cancer staging is critical for prognostication, treatment planning, and determining clinical trial eligibility. Electronic health records (EHRs) have structured staging modules, but physician use is inconsistent. Typically, stage is entered as unstructured free text in clinical notes and cannot easily be used for reporting. Methods: We created an Epic Best Practice Advisory (BPA) decision support tool that requires physicians to enter cancer stage in a structured module. If certain conditions are met, the BPA is triggered as a hard stop, and the physician cannot chart until staging is complete or a reason for not staging is selected. We used Plan, Do, Study, Act methodology to inform the intervention and compared preexisting staging rates to rates at 4, 8, and 12 months postintervention. Results: For 12 months before BPA implementation, 1,480 of 5,222 (28%) patients had cancer stage structured within the Epic problem list. From 1 to 4 months after the BPA 2,057 of 1,788 (115%) cases were staged in Epic. In the 5- to 8-month period after the BPA, 1,057 of 1,893 (56%) cases were staged, and 9 to 12 months after the BPA 1,082 of 1,817 (60%) were staged. Conclusion: Electronic decision support improves the rate of structured cancer staging at our institution. The staging rates between 56% and 60% for the 5- to 8-month and 9- to 12-month periods likely reflect accurate postintervention staging rates, whereas the initial 115% rate for 1 to 4 months is inflated by providers staging cancers diagnosed before the BPA.

Background: The release of ATP from dying cancer cells in response to platinum-based chemotherapy increases extracellular immunosuppressive adenosine (A), which binds to and activates the A2a and A2b receptors on immune cells resulting in an ineffective anti-tumor immune response. Concomitant adenosine receptor blockade may therefore enhance the therapeutic efficacy of some chemotherapeutic agents. AB928, the first clinical-stage small molecule dual adenosine receptor antagonist, is highly potent, pharmacodynamically active, and has been well tolerated in dose escalation studies as a single agent or in combination with chemo/immunotherapy. Methods: ARC-3 (NCT03720678) is a Phase 1/1b, open-label study in participants (pts) with advanced CRC. Phase 1 escalation identified AB928 150 mg orally once daily as the recommended dose in combination with standard mFOLFOX-6. Phase 1b expansion is ongoing and includes at least 15 and up to 40 pts. Eligible pts must have unresectable or mCRC, ECOG performance status 0-1, and at least one RECIST measurable lesion. Phase 1 eligibility included up to 5 lines of prior therapy; Phase 1b is similarly scoped. Exploratory biomarker analyses include immunohistochemistry of the adenosine axis, tumoral next gene sequencing, and tumor/blood immune correlates. Results: As of 27Dec19, 21 pts received AB928 150 mg + mFOLFOX-6: 7 in Phase 1 and 14 in Phase 1b. All previously treated pts (n=12) were FOLFOX- and/or FOLFIRI-experienced. Prior metastatic therapies range from 3 to 5 in Phase 1 escalation and 0 to 3 in Phase 1b expansion. Adverse events (AEs) reported in >30% of pts included fatigue, diarrhea, and thrombocytopenia. AEs related to AB928 occurred in 13 pts and were mostly mild to moderate. AB928-related Grade 3 AEs reported by 3 pts were diarrhea, AST increase, and neutropenia; there were no Grade 4-5 AB928-related AEs. Out of 15 evaluable pts, by investigator assessment, the disease control rate was 100% with 2 partial responses (13%; 1 confirmed, 1 pending confirmation) and 13 stable disease (87%). Of pts with stable disease, 6/13 (46%) had tumor shrinkage >15%. Median time on treatment was 15.4 (range: 1.7 - 40.6+) and 11.9 (range: 2.7 - 15.7+) weeks for Phase 1 and Phase 1b, respectively, with initiation of Phase 1b dosing on 09Sep19. Enrollment up to 40 pts is proceeding based on early efficacy gates; 15 pts are currently receiving study treatment. Conclusions: AB928 with mFOLFOX-6 has been well tolerated without significant evidence of additive toxicity in pts with mCRC. Combination treatment was associated with disease control in all evaluable pts, including those with microsatellite stable and RAS/BRAF mutated mCRC. Additional updates on the safety, clinical activity, and correlative biomarker results for all escalation/expansion pts will be presented. Citation Format: Michael Cecchini, Manuel Modiano, Fadi Braiteh, Olivia S. Gardner, Houston N. Gilbert, Daniel DiRenzo, Lisa Seitz, Matt J. Walters, Fangfang Yin, Rachel Woloski, Melissa C. Paoloni, Ki Y. Chung. Efficacy and safety of AB928 plus modified FOLFOX-6 (mFOLFOX-6) in participants with metastatic colorectal cancer (mCRC): Initial results at the recommended dose for expansion (ARC-3) [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr LB-387.

Background: Gut microbiome composition affects response to PD-1 blockade; and recent proof of concept studies suggest that gut microbiome manipulation is effective in reversing resistance to PD-1 blockade. VE800 is an oral live biotherapeutic consisting of 11 distinct non-pathogenic, non-toxigenic, commensal bacterial strains manufactured in lyophilized form. VE800 induces CD8+ T cell infiltrate into tumors; and significantly enhances anti-tumor activity of PD-1 blockade preclinically in multiple tumor models in a CD103+ dendritic cell and major histocompatibility (MHC) class I dependent fashion (Tanoue et al., 2019). Retrospective analysis of cancer patient's (pt) samples also suggests that greater VE800 strain abundance is associated with improved response to PD-1 blockade. The objective of this phase I study is to evaluate the safety, tolerability, and clinical activity of VE800 administered orally in combination with nivolumab in pts with select cancers. Methods: CONSORTIUM-IO (NCT04208958) is an open-label, first-in-human study evaluating VE800 and nivolumab combination in pts with anti-PD-1/PD-L1 relapsed/refractory melanoma, anti-PD-1/PD-L1 naïve gastric/gastroesophageal junction (GEJ) adenocarcinoma and anti-PD-1/PD-L1 naïve microsatellite-stable (MSS) colorectal cancer. Following a 5-day course of oral vancomycin 125mg QID, VE800 will be administered daily along with nivolumab (480mg Q4W). A single dose level of VE800 will be evaluated. In the interests of maximizing safety, a Simon 2-stage design will be used for each disease cohort. Although no dose-limiting toxicities (DLT) are expected, the first 3 pts will be enrolled serially 1 week apart; and safety data of the first 6 pts will be reviewed prior to further accrual. Pts will continue to receive VE800/nivolumab combination until disease progression or unacceptable toxicity. Primary endpoints include safety, tolerability; and clinical activity by objective response rate (ORR) per RECIST v1.1. Secondary endpoints include duration of response (DOR), disease control rate (DCR), progression-free survival (PFS), overall survival (OS); and metagenomic strain-level analysis of degree/duration of VE800 strain colonization. Exploratory endpoints include tumor and blood immunophenotyping, serum/stool metabolomics and global changes in fecal microbiome composition. CONSORTIUM-IO is currently actively enrolling pts. Citation Format: Diwakar Davar, Judy S. Wang, Michael Cecchini, Zev Wainberg, Martin Gutierrez, Anita Turk, Rose Szabady, Jason Norman, Bernat Olle, Bruce Roberts, Dmitri Bobilev. Consortium-IO: A safety and efficacy study of VE800 in combination with nivolumab in previously treated patients with select advanced metastatic cancers [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr CT246.

e16052 Background: To assess microsatellite instability (MSI) and KRAS mutation prevalence, discrepancies and their impact on outcome in AJCC stage IV colorectal adenocarcinoma (colorectal cancer; CRC). Methods: The 2010-2016 United States National Cancer Database was queried for stage IV CRC patients > 18yo and information on MSI and KRAS mutation. Microsatellite status was stratified as stable microsatellites (MSS, including low instability) and microsatellite instability high (MSI-H). KRAS status was stratified as mutation and wildtype. Prevalence and discrepancies were evaluated according to patient demographics, US geography and CRC factors. Overall survival (OS) was assessed using Cox proportional hazards models adjusting for age, gender, race, comorbidities, metastatic burden, CRC treatment, treatment center type, and year of CRC diagnosis. A priori, a statistical interaction test between microsatellite status, KRAS status and primary CRC site was planned. Results: Microsatellite/KRAS status was available for n = 10,844/n = 25,712 patients, respectively. OS was assessed in n = 5,904 patients with data on both microsatellite and KRAS status, and follow-up. Overall prevalence of MSI-H was 3.1% and KRAS mutation 42.4%. Microsatellite and KRAS status varied according to primary CR site, as presented in Table. Further variation was evident according to US-geography, with MSI-H rates ranging from 1.6% to 4.1%, and KRAS mutation rates ranging from 41.1% to 44%. On multivariable analyses, longer OS was observed in patients with KRAS wildtype versus mutation (HR = 0.91, 95% CI: 0.85-0.97 p = 0.004), MSS versus MSI-H (HR = 0.75, 95% CI: 0.62-0.9, p = 0.003), and left-sided versus right-sided CRC (HR = 0.65, 95% CI: 0.6-0.7, p < 0.001). The effect of KRAS mutation further varied with CRC site and microsatellite status (interaction p = 0.002). Conclusions: Depending on its primary site and US geography, stage IV CRC shows distinct mutational behavior. KRAS mutation, MSI-H, MSI-H and primary CRC sidedness independently affect overall survival and interact with distinct prognostic profiles. Generically classifying adenocarcinomas of different site as “CRC” might deprecate this diversity. [Table: see text]