PSG Score to Predict Response to ¹⁷⁷Lu-PSMA Therapy in mCRPC

Objective: To predict outcomes after 177 Lu–prostate-specific membrane antigen (PSMA) in metastatic castration-resistant prostate cancer (mCRPC) patients using PSMA PET tumor-to-salivary gland ratio (PSG score). Design: Retrospective multi-institutional study. Methods: 237 men with mCRPC treated with 177 Lu-PSMA were included. A quantitative PSG (qPSG) score was semiautomatically calculated on baseline 68 Ga-PSMA-11 PET images using SUV mean ratio of whole-body tumor to parotid glands. Patients were stratified into 3 groups: high (qPSG, >1.5), intermediate (qPSG, 0.5 to 1.5), and low (qPSG, 68 Ga-PSMA-11 PET images and classified patients into 3 groups based on visual PSG (vPSG) score: high (most lesions showed higher uptake than did parotid glands), intermediate (neither low nor high), and low (most lesions showed lower uptake than did parotid glands). Outcome data included a >50% prostate-specific antigen (PSA) decline, PSA progression-free survival (PFS), and overall surviva more...