Dual-Tracer 18F-FDG and 68Ga-PSMA PET/CT Imaging of Heterogeneous Phenotypes of Metastatic Castration-Resistant Prostate Cancer for Predicting Response to Novel Hormone Therapy

PURPOSE: This study evaluated interlesion heterogeneity in prostate cancer using dual-tracer imaging (PSMA and FDG) and explored its predictive value for novel hormone therapy (NHT). PATIENTS AND METHODS: A total of 205 prostate cancer patients (23 biochemical recurrences, 68 metastatic castration-sensitive prostate cancers, 114 metastatic castration-resistant prostate cancers [mCRPC]) who underwent dual 18 F-FDG and 68 Ga-PSMA PET/CT imaging were retrospectively analyzed. Among them, 62 mCRPC patients received NHT. Patients were classified into 3 groups: PSMA+FDG-, PSMA+FDG+, and PSMA-FDG+. SUV ratio , the ratio of PSMA-SUV max to FDG-SUV max , was evaluated for its predictive value on progression-free survival (PFS). RESULTS: The proportion of PSMA+FDG- patients decreased from biochemical recurrence to mCRPC stages, whereas FDG+ cases increased significantly ( P = 0.001). In the NHT cohort, group 3 (PSMA-FDG+) had significantly shorter median PFS than group 1 (133 vs 497 days; P = 0.027). In group 2, patients with a high SUV ratio had better median PFS than those with a low SUV ratio (368 vs 147 days; P = 0.031). CONCLUSIONS: Dual-tracer imaging reveals interlesion heterogeneity in prostate cancer, and SUV ratio may help predict early response to NHT.