Comparative Effectiveness Of Nivolumab (Nivo) Relative To Standard Of Care (Soc) For Advanced/Metastatic (Adv/Met) Gastric Or Gastroesophageal Junction Cancer (Gc/Gejc): A Simulated Treatment Comparison (Stc).

128Background: The prognosis of adv/met GC/GEJC among patients receiving third and later lines (L) of therapy is poor, and effective treatment options are limited. The study objective was to estimate the relative effect of NIVO versus SOC for overall survival (OS), in the US among adv/met GC/GEJC patients who received ≥ 3L therapy. Methods: A STC was performed using individual patient data from the single-arm CheckMate 032 (CM032) trial, and the Flatiron Health (FH) database. Eligible patients had adv/met GC/GEJC and received NIVO (CM032) or SOC (FH) as ≥ 3L therapy; all patients met CM032 eligibility criteria. A regression model of OS was fit to CM032 data using prognostic factors and treatment effect modifiers identified through a systematic literature review. The regression model was used to predict OS for NIVO, using Flatiron patient characteristics as covariates, and to estimate the expected outcome if NIVO had been available in the Flatiron population. The observed and predicted OS for NIVO was comp...