Mature effectiveness and toxicity outcomes associated with three treatment schedules of high-dose-rate brachytherapy monotherapy for favorable-risk prostate cancer.

Purpose: To present long-term toxicity and effectiveness outcomes of three prostate high-dose-rate (HDR) brachytherapy schedules: 38 Gy in 4 fractions, 24 Gy in 2 fractions, and 27 Gy in 2 fractions for men with low- or intermediate-risk prostate cancer.

Methods and materials: Patients treated with HDR brachytherapy monotherapy for prostate cancer were identified in a prospectively maintained, single institution database. Patients with AJCC T-stage ≤ T2b, Gleason score ≤ 7, prostate-specific antigen level ≤ 20 ng/mL, and ≥2 years of follow-up were included.

Results: 671 patients were evaluated. 310 patients received 38 Gy in 4 fractions, 129 received 24 Gy in 2 fractions, and 232 received 27 Gy in 2 fractions. Median follow-up was 12.8 years, 10.6 years, and 8.1 years (p < 0.001), respectively. 231 (74.5%), 92 (71.3%), and 81 (34.9%) patients (p < 0.001) had low-risk disease. Rates of acute grade ≥2 GU toxicity were 11.1%, 12.3%, and 25.0% (p = 0.004), while chronic grade ≥2 GU toxicity were 17.0%, 22.6%, and 26.5% (p = 0.06). For low-risk patients, 10-year overall survival (OS), freedom from biochemical failure (ffBF), local control (LC), and freedom from distant metastasis (ffDM) were 86.6%, 93.3%, 97.9%, and 99.3%. For intermediate-risk patients, 10-year OS, ffBF, LC, and ffDM were 89.5%, 82.6%, 90.5%, and 97.4%. Higher PSA, higher Gleason score, perineural invasion, and 24 Gy or 27 Gy treatment schedules were predictors of biochemical failure.

Conclusions: HDR brachytherapy monotherapy with 38 Gy in 4 fractions was associated with improved long-term ffBF compared with 24 Gy/27 Gy in 2 fractions, without any associated increase in GI or GU toxicity rates.