18F-Fluciclovine PET/CT more likely to change prostate cancer salvage radiotherapy field than 68Ga-PSMA-11.

For men experiencing postprostatectomy biochemical recurrence (BCR) of prostate cancer, accurately identifying the location of recurrence is critical for effective salvage radiation therapy (sRT) planning. Conventional imaging often falls short in localizing subtle disease. Positron emission tomography/computed tomography (PET/CT) using agents like 68Ga-PSMA-11 (targeting prostate-specific membrane antigen) and 18F-fluciclovine (targeting amino acid transport) has emerged as a superior tool to guide sRT, but their comparative impact on treatment decisions needed further assessment.

This secondary analysis of the prospective randomized EMPIRE-2 trial included 140 men (age range, 47-83 years) with detectable prostate-specific antigen (PSA) levels after prostatectomy. Participants were randomized 1:1 to undergo either 18F-fluciclovine PET/CT (arm A, 65 participants) or 68Ga-PSMA-11 PET/CT (arm B, 69 participants). The study compared changes in sRT decisions—specifically, whether to offer radiation therapy and to which field (with or without boost)—between pre- and post-PET time points in each arm, and between the two imaging agents. The Clopper-Pearson binomial method was used for statistical evaluation.

Overall sRT decision changes occurred in 19 of 65 participants (29%) in the 18F-fluciclovine arm (P < .001) and 29 of 69 participants (42%) in the 68Ga-PSMA-11 arm (P < .001). However, there was no statistically significant difference in overall sRT decision changes between the two arms (P = .12). Among participants for whom the final decision was to offer sRT, changes in the specific treatment field (and/or boost) were substantial.

18F-fluciclovine PET/CT led to treatment field changes in 43 of 60 participants (72%) (P < .001), while 68Ga-PSMA-11 PET/CT resulted in changes for 33 of 61 participants (54%) (P < .001). Crucially, 18F-fluciclovine PET/CT was significantly more likely to induce changes in the treatment field or boost compared to 68Ga-PSMA-11 PET/CT (P = .046).