Nivolumab plus chemotherapy in patients with HER2-negative, previously untreated, unresectable, advanced, or recurrent gastric/gastroesophageal junction cancer: 3-year follow-up of the ATTRACTION-4 randomized, double-blind, placebo-controlled, phase 3 trial.

[BACKGROUND] Nivolumab + chemotherapy is now a standard of care for HER2-negative, previously untreated, unresectable or recurrent gastric/gastroesophageal junction cancer (advanced gastric cancer), but long-term follow-up data of clinical trials are limited.

[METHODS] ATTRACTON-4 was a phase 3, double-blind, placebo-controlled trial in Japan, South Korea, and Taiwan. Patients were randomized to either nivolumab or placebo, both combined with the physician's choice of SOX (oral S-1 [tegafur-gimeracil-oteracil potassium] + oxaliplatin) or CAPOX (capecitabine + oxaliplatin). We report the primary endpoints-centrally assessed progression-free survival (PFS) and overall survival (OS)-and landmark analyses of OS among patients alive using 3-year follow-up data.

[RESULTS] At the cutoff date (May 10, 2021), 17/359 patients in the nivolumab + chemotherapy group and 6/358 in the placebo + chemotherapy group were continuing study treatment. PFS (centrally assessed) was longer in the nivolumab + chemotherapy group (median 10.94 vs. 8.48 months; hazard ratio [HR] 0.67, 95% confidence interval [CI] 0.55-0.82). Although OS did not differ between the two groups (median 17.45 vs. 17.15 months; HR 0.89, 95% CI 0.75-1.05), the landmark analysis of OS, calculating HRs at each landmark time point (every month), was getting numerically better in the nivolumab + chemotherapy group over time. Approximately 80% of patients who achieved complete response in the nivolumab + chemotherapy group were alive at 3 years. No new safety signals or major late-onset select treatment-related adverse events were observed for nivolumab + chemotherapy.

[CONCLUSION] This 3-year follow-up of ATTRACTION-4 confirmed the long-term clinical benefit and manageable safety of nivolumab + chemotherapy in patients with previously untreated advanced gastric cancer.

[TRIAL REGISTRATION] NCT02746796.