167 Background: CheckMate 649 (NCT02872116) is a randomized, open label phase 3 study in first line (1L) treatment of pts with advanced GC/GEJC/EAC. Primary analysis results showed statistically significant improvement in overall survival (OS) for NIVO+chemo vs. chemo in all randomized pts. We present HRQOL results for these pts, included as an exploratory study objective. Methods: HRQOL was assessed using EQ-5D-3L (EQ-5D) and Functional Assessment of Cancer Therapy–Gastric Cancer (FACT-Ga). Assessments were performed at baseline (BL), every 6 weeks during treatment and during follow-up. Change from BL EQ-5D Visual Analog Scale (VAS), Utility Index (UI) and FACT-Ga scores were analyzed using mixed models. Time to first symptom deterioration (TTSD), time until definitive deterioration (TuDD), and time to improvement (TTI) were estimated with Kaplan-Meier estimators and stratified Cox models; deterioration/improvement was based on prespecified meaningful change thresholds. Results: 1581 pts were randomized to NIVO+chemo (n = 789) or chemo (n = 792). Among 1359 pts with BL and post-BL patient-reported outcomes (NIVO+chemo, n = 693; chemo, n = 666), BL scores for FACT-Ga total were similar between treatment groups. Least squares mean differences from BL favored NIVO+chemo at most visits for EQ-5D, FACT-Ga total, and Gastric Cancer Subscale (GaCS), and were comparable for other subscales (not shown). TTI generally favored NIVO+chemo (most HR > 1) but was not significantly different between arms. TTSD was longer in NIVO+chemo arm compared with chemo alone (all HRs < 1), except for Emotional Well-Being (WB); only GaCS and FACT-Ga total were significantly different between arms. TuDD showed statistically significant delays in deterioration (HR with CI < 1) for all scores expect Social WB. Conclusions: Compared with chemo alone, the addition of NIVO to chemo maintained HRQoL with a decreased risk of symptom deterioration in patients with previously untreated advanced or metastatic GC/GEJC/EAC. Together with improved OS, these data support NIVO+chemo as a new 1L standard treatment for GC/GEJC/EAC. Clinical trial information: NCT02872116. [Table: see text]
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