Outcome After 68Ga-PSMA-11 versus Choline PET-Based Salvage Radiotherapy in Patients with Biochemical Recurrence of Prostate Cancer: A Matched-Pair Analysis

SIMPLE SUMMARY: In this bi-institutional analysis including 421 patients, we report an overall high biochemical-recurrence free survival rate (58% after three years) after positron-emission tomography (PET)-based salvage radiotherapy (sRT). Additionally, the strong prognostic effect of prostate specific antigen (PSA) level prior to sRT in this patient cohort was observed in multivariate regression analyses. Finally, patients who received staging with two different PET tracers for sRT guidance (cholin vs. prostate specific membrane antigen (PSMA) PET) were compared via propensity score matching and no significant differences in biochemical-recurrent free survival BRFS between the two tracers were observed. ABSTRACT: The purpose of this analysis was primarily to analyze biochemical-recurrence free survival (BRFS) after positron emission tomography (PET)-guided salvage radiotherapy (sRT) in a large cohort, and to further compare BRFS after PSMA vs. choline PET/ computer tomography (CT)-based sRT. This retrospective analysis is based on 421 patients referred for PSMA or choline PET/CT after radical prostatectomy due to biochemically recurrent or persistent disease. BRFS (PSA: 0.2 ng/mL) was defined as the study endpoint. Cox regression analyses were performed to assess the impact of different clinical parameters on BRFS. Additionally, propensity score matching was performed to adjust patient cohorts (PSMA vs. choline PET/CT-based sRT). The median follow-up time was 30 months. BRFS at three years after sRT was 58%. In the multivariate analysis, only PSA before PET imaging and PSA before sRT were significantly associated with BRFS (p < 0.05). After propensity score matching, 272 patients were further analyzed; there was no significant difference in three-year BRFS between patients with PSMA PET-based vs. choline PET-based sRT (55% vs. 63%, p = 0.197). The present analysis confirmed the overall high BRFS rates after PET-based sRT and the strong prognostic effect of PSA level prior to sRT. PSMA PET-based sRT did not have superior BRFS rates when compared with choline PET-based sRT.