SUMMARY: Bile Tract cancer (Cholangiocarcinoma) is a rare and highly aggressive heterogenous cancer, and is the second most common type of primary liver cancer after Hepatocellular carcinoma. It comprises about 30% of all primary liver tumors and includes both intrahepatic and extrahepatic bile duct cancers. It is estimated that approximately 211,000 patients are diagnosed with Biliary Tract cancer and 174,000 patients will die of the disease each year globally. Biliary Tract cancer is most frequently diagnosed in patients between 50 to 70 years old, and 75% of patients are diagnosed at an advanced stage. Klatskin tumor is a type of Cholangiocarcinoma that begins in the hilum, at the junction of the left and right bile ducts. It is the most common type of Cholangiocarcinoma, accounting for more than half of all cases. About 8,000 people in the US are diagnosed with Cholangiocarcinoma each year and approximately 20% of the cases are suitable for surgical resection. Patients diagnosed with Biliary Tract cancer have a very poor prognosis, and the 5-year survival among those with advanced stage disease is less than 10%, with limited progress made over the past two decades. There is therefore an urgent unmet need for new effective therapies.
Patients with advanced Biliary Tract cancers often receive chemotherapy in the first and second line settings, with limited benefit. Gemcitabine and Cisplatin combination is currently the first line standard-of-care treatment. With the recognition of immunogenic features displayed by Biliary Tract cancers, the role of immune checkpoint inhibitors for improving disease control and prolonging survival has been increasingly explored.
KEYTRUDA® (Pembrolizumab) is a fully humanized, Immunoglobulin G4, anti-PD-1, monoclonal antibody, that binds to the PD-1 receptor and blocks its interaction with ligands PD-L1 and PD-L2. By doing so, it unleashes the tumor-specific effector T cells, and is thereby able to undo PD-1 pathway-mediated inhibition of the immune response.
KEYNOTE-966 is a multinational, randomized, double-blind, Phase III trial, conducted to determine whether adding the immune checkpoint inhibitor Pembrolizumab to first line standard chemotherapy, would impact survival outcomes in patients with metastatic or unresectable Biliary Tract cancers. In this study, 1069 patients (N=1069) with advanced and/or unresectable Biliary Tract cancers were randomly assigned to receive Pembrolizumab 200 mg IV every 3 weeks for up to 35 cycles (N=533) or placebo (N=536). Both treatment groups received Gemcitabine 1000 mg/m2 IV on days 1 and 8 every 3 weeks without preset maximum number of cycles, and Cisplatin 25 mg/m2 IV on days 1 and 8 every 3 weeks for up to 8 cycles. The median age was 63.5 years, majority of patients had metastatic disease (88%) and more than half had intrahepatic disease. The Primary endpoint was Overall Survival (OS). Secondary endpoints included Progression Free Survival (PFS), Objective Response Rate (ORR), Duration of Response and Safety. The median follow up was 25.6 months.
The median OS was 12.7 months in the Pembrolizumab group and 10.9 months in the placebo group (HR=0.83; P=0.0034). This represented a 17% reduction in the risk of death in the Pembrolizumab group compared to the placebo group. The 12-month OS rate was 52% with the Pembrolizumab regimen versus 44% for chemotherapy alone and the 24-month OS rates were 24.9% versus 18.1%, respectively. The OS results were generally consistent across subgroups.
There was no significant difference in PFS between the treatment groups but there was a trend toward improved PFS with Pembrolizumab. The median PFS was 6.5 months in the Pembrolizumab arm and 5.6 months in the placebo group (HR=0.87; P=0.23). The estimated 12-month PFS was 25% and 20% respectively.The Objective Response Rates were similar between the two treatment groups – 28.7% in the Pembrolizumab group and 28.5% in the placebo arm.The safety profile of Pembrolizumab was consistent with that observed in previously reported studies and Grade 3-4 adverse events were similar between treatment groups.
The authors concluded that KEYNOTE-966 is the largest randomized Phase III trial in advanced Biliary Tract cancers to date, with more patients enrolled from non-Asian countries. First line treatment with Pembrolizumab plus chemotherapy significantly improved Overall Survival, when compared with chemotherapy alone. The researchers added that one of the limitations of this study is that patients with intrahepatic bile duct cancers were overrepresented in the study population compared with the incidence of the disease in the general population, resulting in smaller sample sizes of patients with extrahepatic and gall bladder sites of origin.
Pembrolizumab in combination with gemcitabine and cisplatin compared with gemcitabine and cisplatin alone for patients with advanced biliary tract cancer (KEYNOTE-966): A randomised, double-blind, placebo-controlled, phase 3 trial. Kelley RK, Ueno M, Yoo C, et al. Lancet. Published online April 16, 2023. https://doi.org/10.1016/S0140-6736(23)00727-4.