Comparative Utility of 68 Ga-FAPI PET/CT and 18 F-FDG PET/CT in Assessing Treatment Response in a Case of Metastatic Anal Melanoma With Brain Involvement.

A 59-year-old man with metastatic melanoma and brain metastases underwent brain radiotherapy. Following treatment, he developed neurological symptoms, prompting further evaluation. To assess the treatment response and possibility of Lutetium-177-FAPI therapy, both 18 F-FDG PET/CT and 68 Ga-FAPI-46 PET/CT scans were performed. The 18 F-FDG PET/CT was inconclusive due to posttreatment changes, making it challenging to distinguish between tumor progression and therapy-related alterations. In contrast, the 68 Ga-FAPI-46 PET/CT revealed multiple areas of increased FAPI uptake, indicative of viable residual lesions and consistent with MRI findings.