Nivolumab (NIVO) + chemotherapy (chemo) vs chemo as first-line (1L) treatment for advanced gastric cancer/gastroesophageal junction cancer/esophageal adenocarcinoma (GC/GEJC/EAC): 5-year (y) follow-up results from CheckMate 649.

398 Background: At 4-y follow-up, 1L NIVO + chemo continued to demonstrate clinically meaningful overall survival (OS) and progression-free survival (PFS) benefit vs chemo with acceptable safety in patients (pts) with advanced non-HER2+ GC/GEJC/EAC from CheckMate 649. We report efficacy and safety results of NIVO + chemo vs chemo at 5-y follow-up. Methods: Adults with previously untreated, unresectable, advanced or metastatic, non-HER2+ GC/GEJC/EAC were enrolled, regardless of programmed death ligand 1 (PD-L1) expression. Pts were randomized to NIVO (360 mg Q3W or 240 mg Q2W) + chemo (XELOX Q3W or FOLFOX Q2W), NIVO + ipilimumab, or chemo. Primary endpoints for NIVO + chemo vs chemo were OS and PFS by blinded independent central review (BICR) in pts with PD-L1 combined positive score (CPS) ≥ 5. Results: Pts were randomized to NIVO + chemo (n = 789) or chemo (n = 792). NIVO + chemo continued to show OS and PFS benefit vs chemo in pts with PD-L1 CPS ≥ 5, pts with PD-L1 CPS ≥ 1, and all randomized pts at 60-month (mo) minimum follow-up (Table). OS rates at 60-mo were higher with NIVO + chemo vs chemo in pts with PD-L1 CPS ≥ 5, pts with PD-L1 CPS ≥ 1, and all randomized pts (Table), and OS benefit with NIVO + chemo continued to be observed in most prespecified subgroups. Objective response rates (ORRs) were higher and responses were more durable with NIVO + chemo vs chemo in pts with PD-L1 CPS ≥ 5, pts with PD-L1 CPS ≥ 1, and all randomized pts (Table). No new safety signals were identified. Conclusions: These results represent the first report of 5-y follow-up for anti–PD-1 + chemo combination therapy in GC/GEJC/EAC to our knowledge. NIVO + chemo continued to provide sustained long-term survival vs chemo with an acceptable safety profile after 5 y of follow-up. These data continue to support the use of NIVO + chemo as a standard 1L treatment for advanced GC/GEJC/EAC. Clinical trial information: NCT02872116 . Efficacy PD-L1 CPS ≥ 5 PD-L1 CPS ≥ 1 All randomized NIVO + chemo(n = 473) Chemo (n = 482) NIVO + chemo (n = 641) Chemo (n = 656) NIVO + chemo (n = 789) Chemo (n = 792) mOS (95% CI), mo 14.4 (13.1–16.2) 11.1 (10.1–12.1) 13.8 (12.4–14.8) 11.4 (10.7–12.3) 13.7 (12.4–14.5) 11.6 (10.9–12.5) HR (95% CI) 0.71 (0.61–0.81) 0.76 (0.67–0.85) 0.79 (0.71–0.88) 60-mo OS rate (95% CI), % 16 (12–19) 6 (4–9) 13 (11–16) 5 (4–7) 12 (10–14) 6 (4–8) mPFS a (95% CI), mo 8.3 (7.0–9.4) 6.1 (5.6–6.9) 7.5 (7.0–8.5) 6.9 (6.2–7.1) 7.8 (7.1–8.6) 6.9 (6.7–7.2) HR (95% CI) 0.71 (0.61–0.82) 0.77 (0.68–0.87) 0.79 (0.71–0.89) ORR a,b (95% CI), % 60 (55–65) 45 (40–50) 60 (55–64) 46 (42–51) 58 (54–62) 46 (42–50) mDOR a,c (95% CI), mo 9.6 (8.3–12.4) 7.0 (5.7–8.0) 8.6 (7.9–10.5) 6.9 (5.8–7.6) 8.5 (7.7–9.9) 6.9 (5.9–7.6) a Per BICR. b In pts with measurable target lesions at baseline. c In all measurable responders. DOR, duration of response; m, median.