Preliminary Outcome of Definitive Radical Radiotherapy for Adenocarcinoma of Prostate in an Era of Intensity-Modulated Radiotherapy: Experience of 564 Patients in a Medical Center in Taiwan

Abstract

Purpose : We here report the preliminary treatment and toxicity outcome of definitive radical radiotherapy for patients with adenocarcinoma of prostate in an era of intensity modulated radiotherapy (IMRT) in our institution and analyze the possible prognostic factors. Materials and Methods : During 2003 and 2010, 564 consecutive patients with adenocarcinoma of prostate receiving radical definitive radiotherapy in our institution were retrospectively reviewed with a median follow-up of 63 months. Among the 542 patients without evident lymphadenopathy (N0) on CT or MRI, there were 97 (17.2%), 181 (32.1%), 214 (37.9%), and 50 (8.9%) in low, intermediate, high, and very high risk groups respectively, based on the National Comprehensive Cancer Network (NCCN) risk classification criteria. Another 22 (3.9%) patients showed regional lymphadenopathy (N1). Median prescription dose was 78 Gy. There were 453 (80.3%) patients receiving androgen deprivation therapy (ADT). Among them, 62 (11.1%) received adjuvant ADT for more than 2 years. Results : The 5-year overall survival (OS), disease specific survival (DSS), distant metastasis free survival (DMFS) and biochemical failure free survival (BFFS) of all patients were 90.3%, 97.9%, 94%, and 87.1% respectively. The 5-year BFFS were 98.2%, 94.6%, 81.2%, and 75.7% for patients of low, intermediate, high, and very high risk groups, respectively. For patients with N1 disease, the 5-year BFFS was down to 49.9%. The difference of BFFS between patients of high and very high risk groups was significant only in those who had MRI for staging. Multivariate Cox regression analysis showed that T-stage, Gleason score, and initial PSA risk groups, and age of 80 or older were significant risk factors of BFFS. Pelvic irradiation significantly increased acute GI toxicity with odds ratio of 1.486 (95% confidence interval 1.059-2.086). Grade 3 or more late toxicity was noted in 23 patients (4.1%) in GU system and 33 patients (5.9%) in GI system. Only 4 (0.7%) patients had persistent GU toxicity and 1 (0.2%) had persistent GI toxicity at the last follow-up date. Multivariate Cox regression showed the mean dose to rectum above 48 Gy to be the only significant factor for late GI bleeding. Conclusions : The treatment outcome of our institution was comparable to published results of IMRT. The higher risk groups of T stage, Gleason score, initial PSA, and age of 80 or older, were significant risk factors for BFFS. Pelvic irradiation modestly increased acute GI toxicity. MRI was more accurate for BFFS prognosis. Late GI bleeding was associated with a mean dose above 48 Gy to the rectum.