Pathological Complete Response following Pembrolizumab Combined with Gemcitabine and Cisplatin Therapy for Initially Unresectable Intrahepatic Cholangiocarcinoma: A Case Report.

INTRODUCTION: Immune checkpoint inhibitors (ICIs) are increasingly used in the treatment of biliary tract cancer; however, reports on conversion surgery following ICI-based therapy for unresectable disease are scarce. CASE PRESENTATIONS: An 83-year-old female was referred to a local hospital for further evaluation after abnormal liver function was detected during a routine health examination. Computed tomography (CT) revealed a 5 cm tumor in segment 4 of the liver, multiple liver metastases in both lobes, and metastasis to lymph node station 8. Biopsy of the tumor confirmed a diagnosis of intrahepatic cholangiocarcinoma, and the disease was determined to be unresectable due to distant metastases. After 10 courses of gemcitabine, cisplatin, and pembrolizumab (GCP) therapy, follow-up CT revealed marked shrinkage of the primary tumor in segment 4 of the liver, liver metastases, and lymph node station 8. Consequently, an extended left hepatectomy with partial resection of segments 6 and 8 was performed. The postoperative course was uneventful, and the patient was discharged on postoperative day 14. Histopathological examination revealed a pathological complete response (pCR). At 4 months postoperatively, the patient was alive without recurrence. CONCLUSION: Reports of conversion surgery following GCP therapy are scarce, and patients achieving a pCR are extremely rare.