469 Background: The Gustave Roussy Immune Score (GRIm-S) considers a composite of neutrophil to lymphocyte ratio (> 6 = 1), albumin (< 35 = 1) and LDH (> ULN = 1) and has been established as a prognostic score and may in aid in the selection of patients for phase 1 trials of immune checkpoint inhibitors. Methods: We explored the prognostic impact of the GRIm-S (high > 1) in patients enrolled on the COMPASS trial and correlated the score with genomic and clinical characteristics. Patients in this trial had biopsies for whole genomic and RNA sequencing prior to standard chemotherapy regimens in the advanced setting. Results: 252 patients were included in the analyses with a median follow-up time of 28 months. 16% of patients had a high GRIm-S with significantly shorter median overall survival (OS) of 4.1 months versus 10.0 months in those with a low score (HR 2.18, 95% CI 1.4-3.4, p < 0.0001). In the GRIm-S-high cohort, early progression with non-evaluable disease and disease progression were more common than in the GRIm-S low cohort (56% vs 31%, p = 0.003). In a multivariable analysis, a high GRIm-S was poorly prognostic (HR 1.6 95% CI 1.3-1.9, p < 0.001), whereas the classical RNA subtype (vs. basal-like) (HR 0.41, 95% CI 0.3-0.6, p < 0.001) and a high HRDetect score (HR 0.47 95% CI 0.3-0.7, p < 0.001) associated with superior OS. The GRIm-S did not correlate with RNA subtypes or with specific KRAS mutations. There were no differences in structural variant load or tumour mutational burden between groups. However those with a high GRIm-S did have a higher total target lesion diameter at baseline (p < 0.001). Conclusions: The GRIm-S identifies a subset of patients who have aggressive pancreas cancer and short life expectancy. This information may help clinicians in treatment decision making and selection for clinical trials.

4057 Background: While several clinical scoring systems exist to aid prognostication and patient (pt) selection for clinical trials in oncology, none are standardly used. We compared the ability of four prognostic scores to predict overall survival (OS) in pts with advanced gastric and esophageal (GE) cancer. Methods: Pts with advanced (unresectable or metastatic) GE cancer receiving first-line palliative-intent systemic therapy at the Princess Margaret Cancer Centre from 2007 to 2020 were included. High prognostic risk pts were identified using four scoring systems: Royal Marsden Hospital (RMH), MD Anderson Cancer Centre (MDACC), Gustave Roussy Immune Score (GRIm-S) and MD Anderson Immune Checkpoint Inhibitor (MDA-ICI) score. OS was estimated using the Kaplan-Meier method and compared between risk groups (high vs. not-high) for each scoring system using the log-rank test. Cox proportional hazards models were used to analyze the association between each prognostic score and OS, adjusting for baseline clinical factors. Harrell’s c-index was used to evaluate predictive discrimination of the models. Time-dependent AUCs were used to measure predictive ability for early death (within 90 days). Results: In total, 451 pts with advanced GE cancer were included. The median age was 59 years, 68% were male, 51% had ECOG status 0-1, 63% presented with de novo metastatic disease. The proportion of pts categorized as high risk was: RMH 25% (N=113), MDACC 13% (N=95), GRIm-S 24% (N=109), MDA-ICI 26% (N=117). In all scoring systems, high risk pts had significantly shorter OS (median OS 7.9 versus 12.2 months for RMH high vs. low risk, p<0.001; 6.8 vs. 11.9 months p<0.001 for MDACC; 5.3 vs. 13 months p<0.001 for GRIm-S; 8.2 vs. 12.2 months p<0.001 for MDA-ICI). On multivariable analysis, each prognostic score was significantly associated with OS (Table). The GRIm-S had the highest predictive discrimination (c-index 0.645 [0.612-0.678]) and highest predictive ability for early death (AUC 0.754 [0.675-0.832]). Conclusions: All four prognostic scoring systems compared had reasonable accuracy in predicting OS for patients with advanced GE cancer. The higher accuracy for predicting early death may render the GRIm-S as preferable. These tools can aid oncologists in discussions about prognosis, therapeutic decision-making and patient selection for clinical trials.[Table: see text]

147 Background: Literature on recurrence and outcomes of HPGEC is scarce. The aim of this study was to determine pattern of recurrence and outcomes after curative intent surgery for locally advanced HPGEC. Methods: A retrospective database was used to identify consecutive patients with gastroesophageal adenocarcinomas undergoing curative intent resection between 2011 and 2016 at the Princess Margaret Cancer Centre. Clinico-demographic data were extracted from the electronic health record. Patterns of relapse are classified as nonvisceral (defined as recurrences in the bone, peritoneal or both), visceral (not nonvisceral, including the brain), or both. Time to relapse (TTR) and overall survival (OS) were calculated from date of histologic diagnosis. Results: Of 45 patients with HPGEC, 78% were male, and 91% were non-Asian. Median age was 64.4 years (interquartile range [IQR] 53, 70); 60% were gastroesophageal junction, 24% were gastric, and 16% were esophageal adenocarcinomas; 31% were poorly differentiated tumors while 68% had clinical or pathological node positive disease. Complete R0 resection occurred in 93%, and 84% had received perioperative therapy (31% with perioperative chemotherapy; 40% with pre-operative chemoradiation; 9% with post-operative chemoradiation). With a median follow-up time of 26.0 months. relapse rate of HPGEC at last follow-up was 78%. Among first relapses, 94% were distant, while 6% were local recurrences. Among distant relapses, visceral recurrences occurred in 85%, nonvisceral in 3%, and 12% patients had both visceral and nonvisceral recurrences. None had peritoneal only recurrence. Median TTR was 12.2 months (IQR 8.8, 23.5), while median post-recurrence survival was 9.7 months (IQR 4.7, 16.3). Of the entire cohort, 2-year OS was 53% and 3-year OS was 26%. Conclusions: More than three-quarters of patients with HPGEC experienced recurrence after curative intent multimodality therapy. Our results suggest that HPGEC rarely relapse with peritoneal only disease or local recurrence, thereby calling into question the utility for aggressive surveillance, pending verification from larger cohorts.