Case Report: From unresectable to resectable: successful conversion therapy with TACE, HAIC, envafolimab, and olaparib in advanced intrahepatic cholangiocarcinoma

Background Intrahepatic cholangiocarcinoma (iCCA) is an aggressive malignancy with poor prognosis, and most patients present with unresectable or metastatic disease. In recent years, approaches such as locoregional therapy, immunotherapy and targeted therapy have achieved significant breakthroughs in the transformation treatment of advanced iCCA. We report a case of successful conversion therapy using envafolimab plus olaparib combined with locoregional therapies in advanced iCCA. Case presentation A 65-year-old male with obstructive jaundice was diagnosed with metastatic iCCA (cT3N1M1, Stage IV) harboring a 117 mm left hepatic lobe lesion, with enlarged lymph nodes, and pulmonary nodules suspicious for metastasis. Next-generation sequencing revealed MSI-H and TMB-H status, along with DDR gene alterations (CDK12 and HDAC2). He received multimodal treatment comprising TACE, HAIC, PD-L1 blockade (envafolimab), and exploratory PARP inhibition (olaparib). Over 20 months, the primary lesion shrank from 117 mm to 42 mm, with regression of lymph nodules and pulmonary nodules and normalization of CA19-9. He underwent R0 resection and pathological examination confirmed a pathological complete response (pCR/ypT0N0) in the resected specimens. At the last follow-up (October 15, 2025), the patient had achieved a progression-free survival of 36 months and a postoperative recurrence-free survival of 16 months. Conclusion This case demonstrates that the TACE plus HAIC combined with PD-L1 blockade and exploratory PARP inhibition is a promising conversion therapy strategy. It provides preliminary evidence for PARP inhibitor therapy in DDR-altered cholangiocarcinoma, supporting further investigation in prospective trials.