(P056) Ten-Year Outcomes of Patients With Gleason Score 9/10 Prostate Cancer Treated With Trimodality Therapy

Andrew T. Wong, MD, A. Sivathayalan, R. Salant, MD, L. Harrison, MD, R. Stewart, MD, T. Carpenter, MD, D. Shasha, MD; Mount Sinai Beth Israel; Carleton University

OBJECTIVE: Multiple publications have reported poor biochemical control in patients with localized Gleason score (GS) 9/10 prostate cancer treated with either surgery or external beam radiation therapy (EBRT). Few studies have specifically addressed brachytherapy outcomes in this cohort or reported outcomes beyond 5 years. The purpose of this study is to report long-term clinical outcomes in patients with GS 9/10 prostate cancer treated with combination EBRT, low-dose-rate brachytherapy (LDRBT), and androgen deprivation therapy (ADT).

MATERIALS AND METHODS: We retrospectively reviewed 73 patients with localized GS 9/10 prostate cancer treated with combination therapy from 1998 to 2012 at a single institution; 27 patients had one high-risk feature (stage T3a/b or PSA ≥ 20 ng/mL), 33 had two features, and 13 had three features. Patients received pelvic EBRT to 50.4 Gy followed by an LDRBT boost (108 Gy ¹²⁵I, 90 Gy ¹⁰³Pd). All implants and contours were performed by a single physician (DS). Luteinizing hormone releasing hormone (LHRH) agonist was given for a median duration of 25 months. Biochemical failure was defined using the Phoenix criteria (PSA nadir + 2). Biochemical progression–free survival (BPFS), prostate cancer–specific survival (PCSS), and overall survival (OS) were calculated using Cox regression analysis. Univariate and multivariate Cox regression was performed to identify factors that may impact BPFS: 1 high-risk feature vs > 1 feature (P = .0358), stage < T3c vs T3c (P = .240), prostate-specific antigen (PSA) < 50 ng/mL vs ≥ 50 ng/mL (P = .753), and isotope ¹²⁵I vs ¹⁰³Pd (P = .471). Toxicity was graded using the Common Toxicity Criteria for Adverse Effects version 3.0 (CTCAE v3.0).

RESULTS: Minimum and median follow-ups were 20 and 55 months, respectively. Five-year actuarial BPFS, PCSS, and OS were 76.4%, 95.1%, and 88.2%, respectively. Ten-year BPFS, PCSS, and OS were 63.4%, 80.5%, and 59.1%. Median time to biochemical failure was 51 months. Multivariate Cox regression analysis showed that a higher number of high-risk features was significant (P = .057), but T3c (P = .378) and PSA ≥ 50 ng/mL (P = .600) were not significant predictors of BPFS. No patients developed acute urinary retention requiring urinary catheterization. One patient developed grade 3 toxicity, and there was no other cases of grade 3/4 genitourinary or gastrointestinal toxicity.

CONCLUSIONS: In this large, retrospective series, we report very good long-term oncologic outcomes and minimal toxicity in patients with GS 9/10 prostate cancer treated with combination EBRT, LDRBT, and ADT. Trimodality therapy is a well-tolerated and effective treatment for these very-high-risk patients.

Proceedings of the 97th Annual Meeting of the American Radium Society- americanradiumsociety.org