Prognostic factors, efficacy, and toxicity of involved-node stereotactic body radiation therapy for lymph node oligorecurrent prostate cancer : An investigation of 117 pelvic lymph nodes.

Abstract

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, 74patients fitted the selection criteria. Atotal of 117 lesions were treated. Median follow-up was 31months (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 asingle target lesion was associated with astatistically significant impact on OS. No in-field recurrence occurred. Patients who reached early prostate-specific antigen (PSA) nadir (< 3months after SBRT) had alower 3‑year survival (p = 0.004). The value of PSA nadir after SBRT and the time between primary treatment and SBRT had an impact on bPFS. Concomitant ADT was associated with improved DPFS. No acute or early late (> 6months) genitourinary and gastrointestinal adverse events of any grade were reported, albeit with relatively short median follow-up. SBRT is asafe and effective treatment for oligorPC, with a100% 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.