A Phase 3 Study of nivolumab (Nivo) in previously treated advanced gastric or gastroesophageal junction (G/GEJ) cancer: Updated results and subset analysis by PD-L1 expression (ATTRACTION-02)

[[abstract]]Background: Nivo monotherapy demonstrated its efficacy with manageable safety for G/GEJ cancer refractory or intolerant to standard chemotherapy at the primary analysis (ATTRACTION-02[ONO-4538-12]: ASCO-GI 2017, Kang YK et al. J Clin Oncol. 2017; 35 [suppl 4S abstract 2]). Here, we report updated results, and the relationship between efficacy of Nivo and PD-L1 expression levels. Methods: 493 patients(pts) aged ≥ 20 years with ECOG PS 0-1 and unresectable advanced or recurrent G/GEJ cancer after failure of two or more previous chemotherapy regimens were randomized in a 2:1 ratio to receive 3 mg/kg Nivo (N = 330) or placebo (N = 163) every 2 weeks until unacceptable toxicity or disease progression. The primary endpoint was overall survival (OS). The PD-L1 expression was assessed by immunohistochemistry (28-8 pharmDx assay). And updated results of the efficacy and safety were based on ≥ 1-year follow-up after last patient enrollment. Results: As of the data cut-off on February 25th 2017, one year after last patient enrollment, the median OS (mOS) was 5.32 months with Nivo versus 4.14 months with placebo (hazard ratio [HR], 0.61; 95% confidence interval [CI], 0.50-0.75; p < 0.0001). The OS rates were 46.4% (95% CI, 40.8-51.8) versus 34.7% (95% CI, 27.4-42.1) at 6 months and 27.6%(95% CI, 22.8-32.6) versus 11.6% (95% CI,7.2-17.1) at 12 months. Immunohistochemistry was performed for exploratory analyses of OS by PD-L1 status on pretreatment tumor biopsies obtained from 197 pts. In pts with PD-L1-positive (expression ≥1%) tumors, the mOS was 5.22 months in the Nivo (16 pts) versus 3.83 months in placebo (10 pts) (HR, 0.58; 95% CI, 0.24-1.38). In pts with PD-L1 negative (