High Dose Rate Brachytherapy as Monotherapy vs. External Beam With HDR Boost in Unfavorable Intermediate Risk Localized Prostate Cancer: A Matched-Pair Analysis.

Abstract

PURPOSE/OBJECTIVE(S)\nBoth high-dose-rate brachytherapy as monotherapy (HDR-M) as well as combined with external beam radiotherapy as a boost (HDR-B) are acceptable treatment approaches for intermediate risk prostate cancer, but data directly comparing relative outcomes of these two approaches for unfavorable intermediate risk (UIR) patients is lacking. This matched-pair analysis compares clinical outcomes for National Comprehensive Cancer Network (NCCN) defined unfavorable intermediate-risk (UIR) patients treated with HDR-M relative to those treated with HDR-B.\n\n\nMATERIALS/METHODS\nPatients with NCCN UIR prostate cancer [Gleason grade group 3, ≥ 50% biopsy cores positive, or ≥ 2 of the following: PSA > 10 and ≤ 20 ng/mL, Gleason score 7, or clinical stage T2b-T2c] were identified in a prospectively maintained, single institution database. Criteria for the matched pair analysis included: 1) age ± 3 years, 2) Gleason Score (minor and major), and 3) clinical T stage. Brachytherapy doses were based on our current institutional standards: 10.5 Gy x 2 for HDR-B and 13.5 Gy x 2 for HDR-M. HDR-B patients received 45-46 Gy in 23-25 fractions EBRT to the prostate, seminal vesicles, and pelvic lymph nodes. Follow-up time was measured from the date of first HDR implant to the date of last recorded follow-up. Biochemical failure was defined as PSA nadir\u202f+\u202f2. Kaplan-Meier method was used to estimate overall survival (OS), cause specific survival (CSS), disease-free survival (DFS), loco-regional recurrence (LRR) and freedom from biochemical failure (FFBF).\n\n\nRESULTS\n51 matched pairs were identified and included in the analysis. HDR-M had a shorter median follow-up time of 39 months vs 100 months in HDR-B (P < 0.001). Race and pre-treatment PSA were well balanced. No significant differences in OS, CSS, or DFS at 1, 3, 5, or 8 years were identified. OS was 100%, 97.9%, 97.9%, 86.8% (HDR-B) vs 100%, 100%, 100%, 85.7% (HDR-M, P\u202f=\u202f0.870). CSS was 100%, 100%, 100%, 94.6% (HDR-B) vs 100%, 100%, 100%, 100% (HDR-M, P\u202f=\u202f0.426). Kaplan-Meier FFBF at 1/3/5/8 years was 100%, 91.7%, 91.7%, 91.7% (HDR-B) vs 95.7%, 92.1%, 92.1%, 92.1% (HDR-M, P\u202f=\u202f0.821). Disease-free survival at 1/3/5/8 years was 82.4%, 76.2%, 76.2%, 76.2% (HDR-B) vs 92%, 88.4%, 88.4%, 88.4% (HDR-M, P\u202f=\u202f0.092).\n\n\nCONCLUSION\nHDR brachytherapy as monotherapy represents a highly effective upfront therapy without the added toxicity of pelvic radiation for appropriately selected UIR prostate cancer patients.