Impact of TOPAZ-1 eligibility on the survival benefit of durvalumab plus gemcitabine–cisplatin in advanced biliary tract cancer: a multicenter real-world study

BACKGROUND: Durvalumab plus gemcitabine-cisplatin (GCD) has become a standard first-line therapy for advanced biliary tract cancer (BTC) following the TOPAZ-1 trial. However, whether the survival benefit observed in trial-eligible patients can be generalized to broader real-world populations remains uncertain. We evaluated the impact of TOPAZ-1 eligibility on the effectiveness of GCD in routine clinical practice. METHODS: In this multicenter retrospective cohort study, 610 patients with unresectable or recurrent BTC treated with first-line GCD (n = 268) or gemcitabine-cisplatin (GC) (n = 342) at 19 Japanese institutions were analyzed. Patients were classified according to TOPAZ-1 eligibility criteria. Overall survival (OS) was compared between treatment groups in the entire cohort and stratified by eligibility status. Multivariable Cox models were constructed separately for eligible and ineligible patients. RESULTS: Among 610 patients, 324 (53.1%) met TOPAZ-1 eligibility criteria. In the overall cohort, GCD was associated with longer OS than GC (median, 13.7 vs 11.3 months; p = 0.009). Among eligible patients, GCD significantly improved OS compared with GC (18.0 vs 13.1 months; p = 0.004), whereas no significant difference was observed among ineligible patients (10.8 vs 10.0 months; p = 0.675). However, the interaction between treatment and TOPAZ-1 eligibility was not statistically significant (p for interaction = 0.162). CONCLUSIONS: In this real-world cohort, the survival benefit of GCD appeared to be primarily observed in patients meeting TOPAZ-1 eligibility criteria. Trial-based eligibility may influence the magnitude of benefit from immunochemotherapy in advanced BTC, underscoring the importance of patient selection in routine practice.