Biochemical failure-free survival of ¹⁸F-rhPSMA-7 and ¹⁸F-flotufolastat PET-guided salvage radiotherapy for patients with recurrent prostate cancer

Prostate-specific membrane antigen (PSMA)-targeted positron emission tomography (PET) has improved localization of prostate cancer (PC) lesions in biochemical recurrence (BCR) for salvage radiotherapy (SRT). We conducted a retrospective review of patients undergoing 18F-rhPSMA-7 or 18F-flotufolastat (18F-rhPSMA-7.3)-PET-guided SRT compared with conventional-SRT (C-SRT) without PET. We evaluated biochemical failure-free survival (bFS) and overall rates of bFS in 110 evaluable patients with recurrent PC after radical prostatectomy who received SRT. 82 patients received 18F-rhPSMA-7/18F-flotufolastat-PET-guided SRT and 28 received C-SRT. Median bFS for patients with 18F-rhPSMA-7/18F-flotufolastat-PET-guided SRT was not reached while median bFS was 45.6 months for patients with C-SRT (p = 0.101). %bFS were 95% (52/55) vs 87% (20/23), 90% (27/30) vs 75% (15/20), 89% (16/18) vs 68% (13/19) and 100% (3/3) vs 57% (8/14) for PET-guided vs C-SRT at 12, 24, 36, and 48 months, respectively. Among patients treated in the prostate bed only, median bFS was not reached for PSMA-PET-guided SRT (n = 52) vs 55.1 months in the C-SRT group (n = 25; p = 0.063). %bFS was greater for PSMA-PET-guided SRT than C-SRT at all evaluated timepoints. 18F-rhPSMA-7/18F-flotufolastat-guided SRT yielded favorable disease outcomes. Although statistical significance was not reached, likely due to the limited sample size in this preliminary analysis, our data illustrate potential for 18F-flotufolastat-PET-guided SRT.