A prospective trial of 68Ga-PSMA and 18F-FDG PET/CT in nonmetastatic prostate cancer patients with an early PSA progression during castration.

Abstract

e17579 Background: To evaluate tumor heterogeneity and burden in nonmetastatic prostate cancer patients with an early PSA progression during castration by 68Ga-PSMA and 18F-FDG PET/CT. Methods: The trial prospectively included 37 patients who had an early PSA progression (≤2ng/ml) during castration, and high-risk (PSADT ≤10 months) nonmetastatic disease by conventional imaging. All patients underwent both 68Ga-PSMA and 18F-FDG PET/CT. Lesions were classified into PSMA-dominant lesions (PSMA+/FDG- and PSMA+/FDG+) and PSMA-/FDG+ lesions according to the tracer uptake status. The primary endpoint was the prevalence of PSMA-/FDG+ disease. Results: All patients were treated with RP (median duration of castration = 23 months). The median PSA at imaging was 0.57ng/ml. Overall, 114 lesions were detected in 29 of the 37 patients. A high prevalence (73%) of N+/M+ disease was observed. Of the 114 lesions, 81 were PSMA-dominant and 33 were PSMA-/FDG+. Per patient level, 9 men (24%, 95%CI: 10%-39%) showed at least one new PSMA-/FDG+ lesions. A short PSADT ( P= 0.009, OR = 8.000) were associated with PSMA-dominant disease, while a high Gleason grade group ( P= 0.022, OR = 13.091) with PSMA-/FDG+ disease. 19 patients (51%) with 51 lesions could be enrolled for oligometastases-directed therapy including 10 PSMA-/FDG+ lesions. Among different disease stages, PSMA-/FDG+ disease was rarely detected in the hormone-sensitive cohort, but frequently found in the castration-resistant cohort. Conclusions: Using 68Ga-PSMA and 18F-FDG PET, we observed a high prevalence of N+/M+ disease and a significant proportion of PSMA-/FDG+ disease in patients with an early PSA progression during castration. (ChiCTR 1900022634). Clinical trial information: 1900022634 . [Table: see text]