In addition, identification of the metabolic activity of the metastatic tumors using [18F]fluorodeoxyglucose (FDG) aids in detecting the aggressive nature of these lesions [57] and allows prediction of their response to PSMA-RLT prior to therapy; lesions that are [18F]FDG-positive but PSMA-negative on PET examination represent more aggressive and metabolically active lesions with worse outcome and response to PSMA-RLT than PSMA-positive but FDG-negative ones [58,59]. Here, FOLH1 is linked to metastatic neoplasm.