Olaparib With or Without Durvalumab for DDR Gene Mutated Biliary Tract Cancer Following Platinum-based Chemotherapy

First-line gemcitabine plus cisplatin chemotherapy is the standard first-line treatment for unresectable or metastatic advanced biliary tract cancer and the optimal duration of the treatment is not mentioned in current clinical guidelines. In the pivotal phase 3 ABC-02 trial, patients received up to 6 to 8 cycles of treatment and stopped without maintenance and our retrospective study shows no significant benefit of continuing gemcitabine plus cisplatin beyond 6 to 8 cycles. However, the survival outcomes of patients who completed 6 to 8 cycles of gemcitabine plus cisplatin without progression are dismal with progression-free survival from the last dose of the treatment of median 5.2 months in a prior retrospective study. Indeed, there is an unmet clinical need in terms of maintenance therapy for advanced biliary tract cancer without progression to first-line gemcitabine plus cisplatin chemotherapy. Durvalumab with/without tremelimumab, anti-CTLA4 inhibitor, showed encouraging results in recently presented study for treatment of advanced biliary tract cancer combination with gemcitabine plus cisplatin. Combination of olaparib and durvalumab showed promising results for metastatic HER-2 negative BRCA mutated breast cancer. For DDR gene mutated advanced biliary tract cancer, olaparib plus durvalumab combination may show synergistic effect with better efficacy than olaparib monotherapy. Both olaparib and durvalumab are relatively well tolerated compared to other cytotoxic chemotherapeutic agents. Olaparib may have some degree of myelosuppression, most patients are expected to well tolerate. Although combination of durvalumab and olaparib may cause additional adverse events, these also might be tolerable, considering that there are no overlapping toxicities between durvalumab and olaparib and the safety data for the combination of durvalumab with olaparib. Considering poor prognosis in patients with advanced biliary tract cancer and lack of maintenance treatment following scheduled first-line GemCis, clinical benefits with maintenance olaparib or olaparib plus durvalumab weigh more than the potential risks.