Complete Pathological Response to Neoadjuvant Chemoimmunotherapy in a Patient With Metastatic Intrahepatic Cholangiocarcinoma With High Tumor Mutational Burden

Intrahepatic cholangiocarcinoma (ICC) is an aggressive biliary tract cancer (BTC) with distinct anatomic, molecular, and clinical characteristics. Over the last 10-20 years, ICC has become the focus of increasing concern largely due to its rising incidence and high mortality rates in various parts of the world, including the United States. Surgery is the only potentially curative treatment option for ICC; however, recurrence rate is high, and prognosis is poor in patients with recurrent disease. The chemotherapy regimen of gemcitabine-cisplatin (GemCis) is still the standard of care for patients with unresectable metastatic ICC. There is limited data regarding pathologic ICC response to palliatively intentioned systemic treatment. Here, we report a case of a 47-year-old Caucasian male with metastatic ICC microsatellite stable (MSS) and TMB 49 mutation per megabase who achieved complete pathological response with sequential GemCis/nab-paclitaxel and pembrolizumab. This case highlights the effect of sequential neoadjuvant chemoimmunotherapy in a patient with high tumor mutational burden (TMB-H) ICC, emphasizing the importance of molecular testing, which provides valuable information that can be used in clinical practice to better select targeted chemotherapy regimens.