Background: Nivolumab, an anti-programmed death-1 agent, showed survival benefits in Asian patients, including Japanese, with gastric/gastro-esophageal junction (G/GEJ) cancer. We report the analysis of the Japanese subpopulation from ATTRACTION-2 that evaluated nivolumab versus placebo in unresectable advanced or recurrent G/GEJ cancer after ≥ 2 chemotherapy regimens. Methods: Data from the Japanese subpopulation in the randomized, double-blind, placebo-controlled, phase 3 trial were analyzed (data cutoff, February 25, 2017). Primary endpoint was overall survival (OS); secondary endpoints included progression-free survival (PFS) and objective response rate (ORR). Results: Among the overall study population of 493 patients, 226 (nivolumab 152; placebo 74) were enrolled from 28 sites in Japan. In the Japanese subset, median OS was longer with nivolumab versus placebo (5.4 months, 95% CI 4.6–7.4 versus 3.6 months, 95% CI 2.8–5.0). The risk of death was lower in the nivolumab versus placebo group (hazard ratio 0.58, 95% CI 0.42–0.78; p = 0.0002). Incidences of serious adverse events were 23% (35/152) and 25% (18/72) in the nivolumab and placebo groups, respectively. In the Japanese ITT population, 22% of nivolumab-treated and 28% of placebo-treated patients received prior ramucirumab treatment. Overall, clinical activity of nivolumab was observed regardless of prior ramucirumab use. In the nivolumab group, ORR and PFS were numerically higher in patients with prior ramucirumab use than in those without. Conclusions: In the Japanese subpopulation, patients receiving nivolumab had longer OS, similar to the overall population, with a manageable safety profile. The interaction between nivolumab and ramucirumab will be clarified in ongoing clinical trials.
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