RATIONALE-305: Clinical Outcomes, Safety Profile, and Practical Use of Tislelizumab + Chemotherapy in Gastric/GEJ Adenocarcinoma

This discussion provides a focused overview of the RATIONALE-305 trial, which evaluated tislelizumab in combination with platinum-based chemotherapy as first-line treatment for patients with previously untreated, HER2-negative gastric or gastroesophageal junction (GEJ) adenocarcinoma. In this global, randomized phase 3 study, the tislelizumab plus chemotherapy arm achieved a median overall survival of approximately 15.0 months compared with about 12.9 months for chemotherapy alone in the intent-to-treat population. An even greater survival advantage was observed in patients with PD-L1–expressing tumors, based on a tumor-area positivity (TAP) score of ≥5%, the trial’s predefined biomarker subgroup. Safety findings were manageable and generally consistent with known profiles of PD-1 inhibitors, with immune-mediated adverse events occurring more frequently in the tislelizumab arm but without new or unexpected toxicities. This segment highlights how the RATIONALE-305 results support tislelizumab-based therapy as an important first-line option for HER2-negative advanced gastric or GEJ adenocarcinoma.