Prostate dose escalation may positively impact survival in patients with clinically node-positive prostate cancer definitively treated by radiotherapy: surveillance study of the Japanese Radiation Oncology Study Group (JROSG).

Objective: To retrospectively analyze outcomes of patients who received definitive pelvic irradiation for clinically pelvic node-positive (cT1-4N1M0) prostate cancer (PCa).

Materials and methods: Clinical records of 148 patients with cT1-4N1M0 PCa treated with definitive pelvic radiotherapy (RT) between 2011 and 2015 were retrospectively collected from 25 institutions by the Japanese Radiation Oncology Study Group. The median age, initial prostate-specific antigen (PSA) level, and biologically effective dose (BED) to the prostate with α/β of 1.5 Gy were 69 (interquartile range [IQR], 65-74.3) years, 41.5 (IQR, 20.3-89) ng/ml, and 177.3 (IQR, 163.3-182) Gy, respectively. All patients underwent neoadjuvant androgen-deprivation therapy (ADT) for a median duration of 10 months. Most patients (141; 95.2%) received concurrent ADT during the irradiation period. The median duration of adjuvant ADT was 16 (IQR, 5-27.8) months. The Phoenix definition was used to assess biochemical failure.

Results: The median follow-up period was 53.5 months (IQR, 41-69.3). The 5-year overall survival (OS) probability was 86.8%. The 5-year biochemical failure-free survival and clinical progression-free survival rates were 69.6% and 76.3%, respectively. Multivariate analysis indicated the BED to the prostate to be a significant prognostic factor for OS. Regarding late adverse events, the estimated cumulative incidences of late Grade 2 or higher gastrointestinal and genitourinary toxicities at 5 years were 8.2% and 5.8%, respectively.

Conclusion: Long-term ADT combined with definitive pelvic external beam RT for cT1-4N1M0 PCa leaded to favorable outcomes. Future prospective studies should validate the suggested survival benefit of local dose escalation to the prostate in this cohort.