Comparative efficacy of tislelizumab + FOLFOX or CAPOX for gastric/gastroesophageal junction adenocarcinoma: an exploratory matching-adjusted indirect comparison

Objective In the RATIONALE-305 trial, first-line tislelizumab + chemotherapy (CAPOX ([capecitabine + oxaliplatin] or 5-fluorouracil [5-FU] + cisplatin) significantly improved overall and progression-free survival (PFS) versus placebo + chemotherapy in unresectable or metastatic human epidermal growth factor receptor 2 (HER2)-negative gastric/gastroesophageal junction cancer (GC/GEJC). This exploratory analysis evaluated the comparative efficacy of tislelizumab + CAPOX versus tislelizumab + CAPOX or FOLFOX (5-FU, leucovorin, oxaliplatin) using a matching-adjusted indirect comparison (MAIC) approach.Methods An unanchored MAIC was performed, weighting individual patient data from RATIONALE-305 (tislelizumab + CAPOX) to match the DisTinGuish Part C (tislelizumab + CAPOX or tislelizumab + FOLFOX) aggregate population. After matching, hazard ratios (HRs) for PFS and odds ratios (ORs) for objective response rate (ORR) were calculated in base-case and sensitivity analyses.Results Baseline characteristics were well balanced post-matching (i.e. weighting). In the base case, compared with tislelizumab + CAPOX, median PFS was numerically longer with tislelizumab + CAPOX or tislelizumab + FOLFOX (7.2 vs. 10.5 months [HR 1.24; 95% CI 0.93–1.65; p = 0.1423]). No statistically significant difference in ORR was observed (48.8% vs. 56.5% [OR, 0.71; 95% CI 0.44–1.15; p = 0.1675], respectively). Sensitivity analyses produced consistent results, supporting the robustness of the base-case findings.Conclusions This exploratory analysis found no statistically significant differences in PFS or ORR between tislelizumab + CAPOX and tislelizumab + CAPOX or FOLFOX. Although median PFS was numerically longer with the mixed chemotherapy backbone, these findings are exploratory in nature and warrant further investigation.Clinical trial registration ClinicalTrials.gov, RATIONALE-305 (NCT03777657); DisTinGuish (NCT04363801)