High-risk prostate cancer treated with I-125 brachytherapy.

Abstract

134 Background: High-risk prostate cancer (HRPC) is commonly defined as Gleason score (GS) ≥ 8, PSA ≥ 20 ng/ml, and/or T3-T4 disease, or having a combination of two intermediate risk factors. Multimodality therapy is commonly utilized for HRPC due to concerns of extra-prostatic extension or seminal vesicle invasion. The purpose of this study was to examine the outcomes of HRPC patients treated with wide brachytherapy implant alone. Methods: From our IRB-approved registry, we performed a retrospective review of all patients with HRPC and no radiographic evidence of metastatic disease who were treated with I-125 prostate brachytherapy at Cleveland Clinic. Patients who received supplemental external beam radiation were excluded. Characteristics analyzed on univariate analysis included initial PSA, GS, clinical stage, use of androgen deprivation (AD), dose to 90% of the prostate (D90), and volume of the gland receiving 100% of the prescribed dose (V100) of 144 Gy. Endpoints included biochemical relapse free survival (bRFS) defined by nadir PSA + 2 ng/ml, and distant metastases. Results: From 7/1997- 6/2011, 389 patients with HRPC were treated with I-125 prostate brachytherapy. Median age was 70 years. Patients with GS 8-10 accounted for 40% of cases, 72% were clinical stage T1c, and the median initial PSA was 11.3 ng/ml. Concurrent AD was utilized in 67% of patients and the median D90 was 144.8 Gy (range 75.7 – 248.33 Gy). At a median follow-up of 27 months, the 5-year bRFS was 75.7% and the 5-year distant metastases-free survival was 93.1%. Nine patients died of prostate cancer (crude rate 2.3%). No clinical or treatment factors were identified that correlated with the development of biochemical failure, including the use of AD (p = 0.19, HR 0.612). Conclusions: Brachytherapy for patients with HRPC yields favorable outcomes at early follow up time. Longer follow-up and prospective studies are needed for further analysis.