Abstract CT078: First-line treatment with sintilimab (sin) vs placebo in combination with chemotherapy (chemo) in patients (pts) with unresectable gastric or gastroesophageal junction (G/GEJ) cancer: Final overall survival (OS) results from the randomized, phase III ORIENT-16 trial

Background: The phase III ORIENT-16 trial evaluated sin (a PD-1 inhibitor) versus placebo plus chemo as first-line (1L) treatment in pts with advanced G/GEJ adenocarcinoma. Sin+chemo previously showed a significant improvement in OS vs chemo in pts with PD-L1 combined positive score (CPS) ≥5 (HR 0.660; 95% CI 0.505-0.864; P=0.0023) and in all pts (HR 0.766; 95% CI 0.626-0.936; P=0.0090), with a median follow-up of 18.8 months (m) at interim analysis (Xu, et al. Ann Oncol 2021). Here we report the results from the final analysis (NCT03745170). Methods: This double-blind, phase III trial enrolled 650 pts ≥18 years of age with untreated, unresectable, locally advanced, or metastatic G/GEJ adenocarcinoma, regardless of PD-L1 expression. Pts were randomized 1:1 to receive sin (3 mg/kg in pts weighing