Oncological outcomes following PSMA PET/CT-guided salvage whole-pelvis radiotherapy for recurrent prostate cancer

Background and purpose: In patients with biochemical recurrence (BCR) after radical prostatectomy (RP), prostate-specific membrane antigen (PSMA) PET/CT can detect early pelvic lymph node metastases, yet optimal management of these recurrences remains unclear. This study evaluates oncological outcomes of patients with BCR after RP and (confirmed or suspected) pelvic lymph node metastases who were treated with PSMA PET/CT-guided salvage whole pelvis radiotherapy (sWPRT) and Androgen Deprivation Therapy (ADT). Materials and methods: This single-centre retrospective analysis included 149 patients undergoing sWPRT and 2-3 years ADT after PSMA PET/CT for BCR following RP ± ePLND (2018-2022). sWPRT was offered to BCR patients with ≤ 6 pelvic PSMA-positive nodes, or to PSMA-negative patients with prior pN1 disease. Outcomes included biochemical progression-free survival (bPFS), metastasis-free survival (MFS), treatment-free survival (TFS), overall survival (OS), and cancer-specific survival (CSS). Multivariate Cox regression identified predictors of biochemical progression. Recurrence locations on PSMA PET/CT were recorded and correlated with radiotherapy fields. Results: After a median 54-month follow-up, 5-year bPFS, MFS, TFS, OS and CSS were; 69.3%, 79.0%, 78.5%, 91.7% and 97.5%. Outcomes did not differ between PSMA-negative and PSMA-positive subgroups. Biochemical progression occurred in 37 patients (25%), with rare in-field recurrences (1/37) and predominantly out-field nodal recurrences (29/37). Higher pre-sWPRT PSA (HR = 3.88, p = 0.021) and longer ADT duration (HR = 0.92, p < 0.001) independently predicted biochemical progression. Conclusion: PSMA PET/CT-guided sWPRT with ADT provides good in-field tumour control and good 5-year oncological outcomes in patients with BCR following RP. PSA prior to sWPRT and ADT duration were significant predictors for bPFS.