Perioperative tislelizumab plus chemotherapy for locally advanced gastric cancer: A randomized, prospective phase 2 trial.
Adding perioperative tislelizumab to chemotherapy raised the major pathological response rate in tsMHC-II-positive operable locally advanced gastric or gastroesophageal junction cancer (61.8% vs. 26.5%, p = 0.003), meeting the primary endpoint of the phase 2 Mountain-02 trial in 136 patients. No significant benefit appeared in tsMHC-II-negative patients, and tsMHC-II positivity also tracked with higher pCR (32.4% vs. 5.9%). The results position tumor-specific MHC class II expression as a candidate biomarker for selecting patients for perioperative immunotherapy.
Why it matters: Identifies a predictive biomarker that separates responders from non-responders to perioperative immunotherapy in gastric cancer.