CTLA4 and cholangiocarcinoma: In a multicenter phase II study involving 39 cases of metastatic BTC (16 intrahepatic CCA, 10 extrahepatic CCA, 13 gall bladder cancer), the combination of nivolumab (anti-PD-1 inhibitor) and ipilimumab (anti-CTLA-4 inhibitor) was investigated.