Outcomes of Radiation Therapy for Clinically Node-Positive Prostate Cancer: Surveillance Study of the Japanese Radiation Oncology Study Group (JROSG)

To retrospectively analyze the outcomes of radiation therapy for clinically pelvic node-positive (cT1-4N1M0) prostate cancer. Clinical records of 169 patients with cT1-4N1M0 prostate cancer treated with definitive radiotherapy between 2011 and 2015 were retrospectively collected from 24 institutions by the Japanese Radiation Oncology Study Group. The median age was 69 years (range, 46-93). The median initial prostate specific antigen (PSA) level was 20.6 ng/ml (range, 2.05-914). Gleason’s scores were as follows; 6 in 1, 7 in 30, 8 in 54, 9 in 75 and 10 in 9 patients. One hundred forty-six (86.4%) and 23 (13.6%) patients had received whole pelvic radiotherapy and prostate-only radiotherapy, respectively. The median biologically effective dose (BED) with α/β of 1.5 Gy was 172.7 Gy (range, 133-242.7). All patients underwent 9 months (median) of neoadjuvant plus concomitant androgen-deprivation therapy (ADT), followed by adjuvant ADT with a median duration of 24 months. Regarding biochemical failure for this survey, the Phoenix definition for PSA failure was used. The median follow-up period was 53 months (range, 9-99). Estimated 5-year overall and progression free survival rates were 84.6% and 69.3%, respectively. Fifty-one (30.2%) and 35 (20.1%) patients developed biochemical recurrence and clinical relapse, respectively. The median intervals from the completion of radiotherapy until PSA failure and clinical relapse were 27 months (range, 1-86) and 25.5 months (range, 3-89), respectively. Pelvic lymph node recurrence was observed in 11 patients and distant metastases in 22. The metastatic lymph node recurrence rates in the radiation field in patients who underwent whole pelvis radiotherapy was 4.8% (7 patients), while being 17.4% (4) in those treated with prostate-only radiotherapy. The univariate analyses revealed that number of lymph nodes, BED and boost irradiation to pelvic lymph nodes were significant factors impacting overall survival (OS). Multivariate analyses revealed BED to be the only significant prognostic factor for OS (p = 0.01). Regarding late adverse events, 12 (7.1%) and 11 (6.5%) patients experienced grade 2 or higher gastrointestinal and genitourinary toxicities, respectively. This survey revealed the current pattern of practice status for radiotherapeutic approaches employed for clinically pelvic node-positive prostate cancer in Japan. The results of the present investigation suggest that local dose-escalated radiotherapy would improve outcomes for clinically pelvic node-positive prostate cancer.