Durable response after discontinuation of pembrolizumab therapy for intrahepatic cholangiocarcinoma: a case report.

Although it has recently been reported that immune checkpoint inhibitors (ICIs) constitute effective treatment for solid tumors, the success rate in patients with intrahepatic cholangiocarcinoma is limited. We administered pembrolizumab to a patient as treatment for liver and lymph node metastases of intrahepatic cholangiocarcinoma. The patient had abundant infiltration of programmed death ligand 1-positive macrophages, cytotoxic T cells (CD8-positive lymphocytes), and programmed death 1-positive lymphocytes as well as a high combined positive score of 33.1, high-frequency microsatellite instability, and mismatch repair deficiency. These characteristics are predictive biomarkers of the efficacy of ICIs. After pembrolizumab was administered four times (triweekly administration), the carbohydrate antigen 19-9 serum level fell within the normal range, and computed tomography revealed that the size of the metastatic liver tumors and enlarged hilar lymph node had markedly decreased. However, the patient developed pruritus and exanthema on the trunk and limbs after 14 administrations and was diagnosed with bullous pemphigoid. We discontinued pembrolizumab therapy and started treatment for bullous pemphigoid. Nine months after discontinuation of pembrolizumab therapy, the patient remains alive without tumor relapse. This patient had durable response even after discontinuation of pembrolizumab therapy for multiple metastases of intrahepatic cholangiocarcinoma.