The discussion turns to the TOPAZ-1 study design and its long-term efficacy update. The faculty review the phase 3, randomized, double-blind, placebo-controlled structure of the trial, which enrolled previously untreated patients with unresectable or metastatic biliary tract cancer and randomly assigned them to durvalumab plus gemcitabine and cisplatin or to placebo plus gemcitabine and cisplatin. They walk through the treatment schedule, noting that the chemotherapy backbone was capped at a fixed number of cycles, that durvalumab or placebo continued as monotherapy after chemotherapy completion, that crossover was not permitted, and that overall survival served as the primary end point. The panel places the chemotherapy cap in practice context, observing that transitioning to immunotherapy alone is consistent with practice and may help preserve quality of life. The faculty also address how the trial demographics map to the patients they treat, noting the regional variation in the proportion of Asian patients compared to the study and that baseline characteristics are otherwise representative of their practice. Reviewing the extended follow-up analysis, the panel describes a sustained overall survival advantage with the addition of durvalumab. The faculty interpret the data as evidence that a subset of patients derives durable benefit from checkpoint inhibition, and they raise the unresolved question of how they can identify who those patients are.
