High Dose Rate Brachytherapy as Monotherapy vs. External Beam With HDR Boost in Unfavorable Intermediate Risk Localized Prostate Cancer: A Matched-Pair Analysis
International Journal of Radiation Oncology, Biology, Physics
Both 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.
Patients 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 + 2. 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).
51 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 = 0.870). CSS was 100%, 100%, 100%, 94.6% (HDR-B) vs 100%, 100%, 100%, 100% (HDR-M, P = 0.426). 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 = 0.821). 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 = 0.092).
HDR brachytherapy as monotherapy represents a highly effective upfront therapy without the added toxicity of pelvic radiation for appropriately selected UIR prostate cancer patients.
Challapalli A, Masson S, Humphrey P, Bamisaye F, Jacobs P, French C, Bahl A. High dose rate brachytherapy as monotherapy for localized prostate cancer: Our initial experience. JCO [Internet]. 2016;34(2):e626. Available from: https://doi.org/10.1200/jco.2016.34.2_suppl.e626