First-line (1L) nivolumab (NIVO) plus chemotherapy (chemo) vs chemo in patients (pts) with advanced gastric cancer, gastroesophageal junction cancer, and esophageal adenocarcinoma (GC/GEJC/EAC): CheckMate 649 Chinese subgroup analysis with 3-year follow-up.

353 Background: NIVO + chemo demonstrated clinically meaningful improvement in overall survival (OS) and an acceptable safety profile vs chemo in previously untreated Chinese pts from CheckMate 649, consistent with the overall study population with advanced GC/GEJC/EAC. Results from CheckMate 649 led to approval of 1L NIVO + chemo in multiple countries, including China. We report 3-year follow-up results in Chinese pts. Methods: Adults with previously untreated, unresectable advanced or metastatic, non-HER2-positive GC/GEJC/EAC were enrolled regardless of programmed death ligand 1 (PD-L1) expression. Randomized pts received NIVO (360 mg Q3W or 240 mg Q2W) + chemo (XELOX Q3W or FOLFOX Q2W), NIVO + ipilimumab, or chemo. Dual primary endpoints for NIVO + chemo vs chemo were OS and progression-free survival (PFS) by blinded independent central review (BICR) in pts with PD-L1 combined positive score (CPS) ≥ 5. Results: 208 Chinese pts were randomized to NIVO + chemo or chemo. At 37 month (mo) minimum follow-up, NIVO + chemo continued to demonstrate clinically meaningful improvement in OS and PFS vs chemo in pts with PD-L1 CPS ≥ 5 and in all randomized pts. The 36-mo OS rate was 31% with NIVO + chemo vs 11% with chemo in pts with PD-L1 CPS ≥ 5 and 26% vs 9% in all randomized pts, respectively. Objective response rate (ORR) (95% CI) per BICR in pts with PD-L1 CPS ≥ 5 who had measurable lesions at baseline was 68% (56-79) with NIVO + chemo and 48% (36-60) with chemo, and in all randomized patients was 66% (55-76) and 45% (35-56), respectively. Responses were more durable with NIVO + chemo vs chemo in pts with PD-L1 CPS ≥ 5, with median duration of response (mDOR) (95% CI) of 12.5 mo (7.2-23.4) vs 6.9 mo (3.9-8.5); in all randomized pts, mDOR was 12.5 mo (7.2-17.7) vs 5.6 mo (4.4-8.3), respectively. No new safety signals were identified. Conclusions: After 3 years of follow-up, NIVO + chemo continued to demonstrate clinically meaningful survival benefit and durable objective responses vs chemo in Chinese pts, with an acceptable safety profile, consistent with the overall study population with advanced GC/GEJC/EAC. These results further support NIVO + chemo as a 1L treatment option for Chinese pts. Clinical trial information: NCT02872116 . [Table: see text]