Efficacy and Safety Analyses of Cytoreductive Non-Regional Lymph Node Radiotherapy in Addition to Prostate-Directed Local Therapy in Low Metastatic Burden Prostate Cancer

Abstract

Abstract Background To evaluate the efficacy and safety of cytoreductive non-regional lymph node radiotherapy (NRLNRT) in addition to prostate-directed local therapy (PDLT) in low metastatic burden prostate cancer (LMBPC). Methods From August 2009 to February 2021, 88 LMBPC patients with NRLN metastasis were identified. Patients receiving cytoreductive NRLN RT in addition to PDLT (NRLN RT group) were matched by one-to-one propensity score to patients without cytoreductive NRLN radiotherapy (control group). Kaplan-Meier method and Cox proportional hazards model were used for prognostic analyses. Results The median follow-up was 43.3 months. PSA response after NRLN RT was 70.6%, and the median PFS after NRLN RT was 29.5 months. The 4-year OS for NRLN RT group and control group was 62% and 46%, respectively (P = 0.037). NRLN RT (HR 0.22, P = 0.001), HSPC (HR 0.32, P = 0.003), bone metastases (HR 3.79, P = 0.000) and androgen-receptor-axis-targeted agents (HR 0.40, P=0.007) were independent prognostic factors of OS. Subgroup analyses showed HSPC at the time of NRLNM and patients with ＜5 NRLNM had greater magnitude of benefit than the counterpart (HR 0.28, 95% CI 0.08-0.94, P= 0.039; HR 0.16, 95% CI 0.04-0.69, P = 0.014). After PSM, NRLN RT was still associated with improved OS (HR 0.39, 95% CI 0.16-0.96, P = 0.040). NRLN RT related AEs were 11 cases (32.4%) of acute gastrointestinal AEs, 3 cases (8.8%) of acute skin AEs, 10 cases (29.4%) of acute bone marrow suppression (BMS) and 5 cases (14.7%) of chronic BMS. All were grade 1-2 AEs. Conclusions It was beneficial and safe to apply cytoreductive NRLN radiotherapy in addition to PDLT in LMBPC. HSPC at the time of NRLNM and patients with < 5 NRLNM may be the potential beneficiaries. Prospective studies were needed for verification.