Imaging screening with [68Ga]-Ga-PSMA-11, [18F]F-FDG, and [18F]-FCholine PET/CT for [177Lu]-PSMA radioligand therapy eligibility in mCRPC

Abstract

Objective

To assess [18F]F-FDG (FDG) and [18F]-Fcholine (Fcholine) performance for discordant lesion detection with [68Ga]-Ga-PSMA-11 (PSMA) PET/CT for [177Lu]-PSMA (LuPSMA) radioligand therapy eligibility in metastatic castration-resistant prostate (mCRPC).

Method

This multicenter retrospective study included adults who performed FDG, FCholine and PSMA PET/CT before LuPSMA (I&T or 617) radioligand therapy in mCRPC. PSMA and FDG PET/CT were performed within 30 days and FDG and FCholine within 45 days. During this time, the French regulatory agency required the use of Fcholine prior to performing a PSMA PET/CT. Imaging analysis on a lesion-based level was performed by two groups of readers with different imaging reading order (Group 1: PSMA, FDG and Fcholine. / Group 2: PSMA, Fcholine and FDG). The primary outcome was the percentage rate of patients with discordant findings between PSMA- and FDG-PET (PSMA-FDG) and between PSMA- and Fcholine-PET (PSMA-Fcholine). The secondary outcome was the concordance and discordance rate between FDG and Fcholine PET.

Results

A total of 60 patients (median age, 74 years [IQR, 68–79 years]) were included between May 2021 and June 2022. 57/60 (95%), 35/60 (57%), 20/60 (33%) patients had bone, lymph node, and visceral disease on PSMA PET/CT. PSMA-FDG discordance was found in 16/60 (26%) patients and discordant lesions were detected in viscera, lymph nodes and bone in 5/16 (31%), 8/16 (50%), 9/16 (56%) patients, respectively. PSMA-Fcholine discordance was found in 18/60 (30%) patients. None of the patients had discrepant visceral lesions (0/18), while 8/18 (44%), 13/18 (72%) patients presented discordant findings for lymph nodes and bone metastases on Fcholine. Among patients with PSMA-FDG discordance, 8/16 (50%) also showed discordance in PSMA-Fcholine analysis. PSMA-Fcholine discordance not detected by PSMA-FDG analysis was observed only in bone in 8/18 (44%) patients and in lymph nodes in 2/18 (11%) patients.

Conclusion

Compared to FDG, Fcholine PET/CT did not detect discordant visceral lesions in patients with mCRPC being considered for LuPSMA radioligand therapy. Prognostic significance of bone-only lesions detected by Fcholine PET/CT requires further evaluation.