Tumor Mutational Burden-High Intrahepatic Cholangiocarcinoma Presenting with Solitary Brain Metastasis: A Case of Precision Oncology.

INTRODUCTION: Brain metastasis from intrahepatic cholangiocarcinoma (ICC) is a rare condition with a poor prognosis, and no standard treatment has been established. This report aims to present a case of solitary ICC brain metastasis successfully treated with a multimodal approach guided by comprehensive genomic profiling (CGP). CASE PRESENTATION: A 64-year-old man, who had undergone a left hepatectomy for ICC 15 months prior, presented with recent memory difficulties. A brain MRI revealed a solitary 39-mm ring-enhancing mass in the left temporal lobe. The patient underwent surgical resection of the brain tumor, and histological examination confirmed the lesion was a metastasis from the primary ICC. Postoperatively, he received systemic therapy consisting of gemcitabine, cisplatin, and durvalumab. CGP on the resected brain specimen revealed a high tumor mutational burden status (23 mutations/Mb) and microsatellite stability. At the 8-month follow-up after the craniotomy, the patient remains disease-free with no signs of recurrence. CONCLUSIONS: This case suggests that an integrated approach, combining aggressive local therapy with systemic immunotherapy informed by biomarkers, can achieve a favorable outcome in selected patients with ICC. The identification of a high tumor mutational burden was crucial in guiding treatment and supports its potential as a predictive biomarker. This precision oncology strategy may improve the poor prognosis associated with this condition.