Prostate-Specific Membrane Antigen Positron Emission Tomography-Detected Intrahepatic Cholangiocarcinoma in a Patient With Metastatic Castration-Resistant Prostate Cancer: Dual Cancer Management With Pluvicto and Intensity-Modulated Radiation Therapy.

Intrahepatic cholangiocarcinoma (ICC) is a rare hepatobiliary malignancy often diagnosed at advanced stages due to its silent progression. Prostate-specific membrane antigen (PSMA) PET/CT, primarily used in prostate cancer, can incidentally detect unrelated malignancies. In a patient with metastatic castration-resistant prostate cancer (mCRPC), PSMA PET/CT revealed a liver lesion initially presumed metastatic. However, lack of uptake on post-therapy single-photon emission computed tomography/CT (SPECT/CT) prompted further evaluation, and MRI with biopsy confirmed ICC. The patient received intensity-modulated radiation therapy (IMRT) for ICC, stereotactic body radiation therapy (SBRT) for prostate metastases, and continued Lu-177 PSMA-617 therapy. This case highlights the incidental diagnostic value of PSMA PET and the importance of post-therapy imaging and multidisciplinary care in managing complex cancer presentations.