Real-World Outcomes Of First-Line Us Patients With Unresectable Advanced Or Metastatic Gastroesophageal Adenocarcinoma By Primary Tumor Location

304 Background: Gastric cancer clinical trials are inconsistent in their inclusion of esophageal adenocarcinoma (EAC). Thus it is uncertain if outcomes are similar among subgroups of gastroesophageal adenocarcinoma. The aim of this study was to compare baseline characteristics and clinical outcomes of US patients with EAC versus Gastroesophageal Junction Cancer (GEJC) and Gastric Cancer (GC) treated in real world clinical settings. Methods: Adult patients with unresectable, advanced or metastatic GC, GEJC, or EAC diagnosed between January 2011 and November 2018 were identified from the Flatiron Health database. Patients with a positive HER2 test, or who received trastuzumab, were excluded. Overall survival (OS) was defined as time from first-line (1L) treatment initiation to death or loss of follow-up. Survival analyses were conducted using Kaplan-Meier methods with log-rank test and Cox models. Results: A total of 3052 patients (969 EAC and 2083 GEJC/GC) met eligibility criteria. Out of all EAC patients, 90% were males and 76% were white. Within the GEJC/GC patients, 67% were males and 57% were white. Median age was 66 years for both cohorts while proportion with ECOG PS of 0 or 1 was 78% for EAC and 84% for GEJC/GC among patients with ECOG scores. The proportion of patients receiving 1L treatment was comparable (78% for EAC, 76% for GEJC/GC) across groups with FOLFOX being the most frequent treatment (25% for EAC and 29% for GEJC/GC). There was no significant difference in OS between the two groups, with median OS of 9.1 and 9.6 months for EAC and GEJC/GC, respectively (HR 0.957, 95% CI: 0.863 - 1.062, p = 0.41). Conclusions: In this US real-world analysis, OS did not differ significantly between patients with EAC and patients with GEJC/GC who received 1L treatment, suggesting that these two populations may have comparable survival benefit from systemic therapy.