The optimal radiotherapy regimen is not yet defined in the setting of oligorecurrent prostate cancer (oligorPC). There is evidence of high variability in treatment protocols among different centers worldwide, and no international consensus guidelines on treatment volumes, radiation schedules, and techniques. The purpose of the present retrospective study is to evaluate the efficacy and safety of involved-pelvic-node stereotactic body radiotherapy (SBRT) for oligorPC.
Patients with pelvic node oligorPC following primary surgery, radical radiotherapy, or salvage radiotherapy for biochemical or local relapse of prostate cancer who underwent involved-node SBRT with biological effective dose (BED) > 100 Gy, with or without concurrent and adjuvant androgen deprivation therapy (ADT), were retrospectively evaluated. Biochemical progression-free survival (bPFS), distant progression-free survival (DPFS), overall survival (OS), possible prognostic factors, and toxicity outcomes were investigated.
From November 2012 to December 2019, 74 patients fitted the selection criteria. A total of 117 lesions were treated. Median follow-up was 31 months (range 6-89). Concurrent ADT was administered in 58.1% of patients. The 1‑year, 2‑year, and 3‑year DPFS was 77%, 37%, and 19%, respectively; the 1‑year, 2‑year, and 3‑year OS was 98%, 98%, and 95%, respectively. The presence of a single target lesion was associated with a statistically significant impact on OS. No in-field recurrence occurred. Patients who reached early prostate-specific antigen (PSA) nadir ( 6 months) genitourinary and gastrointestinal adverse events of any grade were reported, albeit with relatively short median follow-up.
SBRT is a safe and effective treatment for oligorPC, with a 100% local control rate in our series. It is not possible to clearly assess the opportunity to postpone ADT prescription in patients with two or more nodal metastases. The number of secondary lesions, time-to-nadir PSA, PSA nadir value, and the time interval between primary treatment and SBRT were identified as prognostic factors. Future prospective randomized studies are desirable to better understand the still open questions regarding the oligorecurrent prostate cancer state.

© 2021. The Author(s), under exclusive licence to Springer-Verlag GmbH Germany.