ATM expression as a prognostic marker in patients with advanced biliary tract cancer treated with first-line gemcitabine and platinum chemotherapy

Background/Aim: Biliary tract cancer (BTC) has a poor prognosis due to its highly invasive and metastatic potential. Ataxia-telangiectasia mutated (ATM) is a key regulator of DNA damage response and an emerging therapeutic target; however, the association between the expression of ATM and the prognosis in advanced BTC is unknown. We aimed to identify the relationship between ATM expression, clinicopathological characteristics, and survival outcomes in patients with advanced BTC. Patients and Methods: We analyzed 113 patients with advanced BTC who received first-line gemcitabine and platinum. Results: The tumor location was intrahepatic cholangiocarcinoma (IHCCC) in 43 patients, extrahepatic cholangiocarcinoma (EHCCC) in 49, and gallbladder (GB) cancer in 21 patients. Fifty-four patients (47.8%) exhibited loss of ATM protein expression. The overall response rate (ORR) of ATM loss and intact ATM was 13.3% and 19.6%, respectively. In a subgroup analysis, EH-CCC patients with ATM loss tended to have improved PFS after platinum-based chemotherapy compared to those with intact ATM (7.9 vs. 6.2 months, respectively; p=0.050). Conclusion: We demonstrated that ATM loss could be a prognostic marker after platinum-based chemotherapy in patients with advanced EH-CCC.