A phase III study of nivolumab (Nivo) in previously treated advanced gastric or gastric esophageal junction (G/GEJ) cancer (ATTRACTION-2): Three-year update data.

383 Background: Nivo is the first immune checkpoint inhibitor (ICI) to show efficacy and tolerability in G/GEJ cancer patients refractory to or intolerant of standard chemotherapy. Although Nivo has demonstrated durable efficacy in several cancer types, no long-term efficacy data in G/GEJ cancer has been reported to date. Here, we report the 3-year survival data of Nivo in G/GEJ cancer. Methods: A total of 493 patients with unresectable advanced or recurrent G/GEJ cancer after the failure of two or more chemotherapy regimens were randomized in a 2:1 ratio to receive 3 mg/kg Nivo (N = 330) or placebo (N = 163) until disease progression or unacceptable toxicity. The primary endpoint was overall survival (OS). Updated results of the efficacy and safety were based on ≥ 3 years of follow-up after last patient enrollment. In subgroup analysis, we evaluated OS by BOR and incidence of select treatment-related adverse events (TRAEs). Results: As of data cut-off in February 2019, 3 years after last patient enrollment, the hazard ratios of OS and PFS in the Nivo group compared with the placebo group remained 0.62 and 0.60, respectively. The 36-month OS rates of Nivo and placebo were 5.6% and 1.2 % and the 36-month PFS rates were 2.4% and 0%, respectively. In the OS subgroup analysis by BOR, the median OS and 3-year OS rate in CR/PR patients with Nivo were 26.7 months and 35.5%, respectively. The incidence rate and severity of TRAEs were comparable with those of the 2-year cut-off. In the OS subgroup analysis based on the presence or absence of select TRAEs, the hazard ratio in patients with select TRAEs was 0.46 compared to those without select TRAEs. We are analyzing the baseline characteristics that are associated with long-term survival with Nivo. Conclusions: Nivo showed durable efficacy and a good safety profile on long-term follow-up in heavily pretreated G/GEJ cancer patients. Clinical trial information: NCT02267343.