Outcomes Associated With 3 Treatment Schedules of High-Dose-Rate Brachytherapy Monotherapy for Favorable-Risk Prostate Cancer.

Purpose: We report the outcomes associated with 3 high-dose-rate (HDR) brachytherapy regimens used as monotherapy for favorable-risk prostate cancer.

Methods And Materials: Four hundred ninety-four patients with stage ≤T2b prostate cancer, Gleason score ≤7, and prostate-specific antigen levels ≤15 ng/mL underwent HDR brachytherapy as monotherapy. Of those, 319 received 38 Gy in 4 fractions, 79 received 24 Gy in 2 fractions, and 96 received 27 Gy in 2 fractions. Acute and chronic genitourinary (GU) and gastrointestinal (GI) toxicities were defined as side effects occurring ≤6 and >6 months, respectively, after radiation therapy (RT) and were graded according to the Common Terminology Criteria for Adverse Events version 3.0. The time to toxicity was calculated from the date of RT completion. Variables were analyzed with χ(2) test. P values <.05 were considered significant.

Results: The median overall follow-up time was 4 years (range, 5.5, 3.5, and 2.5 years for 38 Gy, 24 Gy, and 27 Gy, respectively, P<.001). Acute and chronic grade ≥2 GU and GI toxicity profiles were similar among groups. Acceptable rates of grade 2 GU toxicities were seen with overall acute/chronic frequency/urgency, dysuria, retention, incontinence, and hematuria rates of 14%/20%, 6%/7%, 7%/4%, 1.5%/2%, and 1.5%/7%, respectively. Minimal grade 3 and no grade 4 or 5 toxicities were seen. Grade 1, 2, and 3 chronic urethral stricture rates were 0.3%, 2%, and 1%, respectively. All GI toxicities were similar between groups, with overall rates of acute/chronic grade 2 diarrhea, rectal pain/tenesmus, rectal bleeding, and proctitis of 1%/1%, <1%/0.5%, 0%/2%, and <1%/1%, respectively. No grade 3, 4, or 5 toxicities were seen. All comparisons were similar for hormone-naïve patients. The median time to maximal GU/GI toxicity was similar between groups, ranging from 1 to 1.6 to 0.9 to 1.2 years, respectively. There were no differences in clinical outcomes between the 3 groups at 5 years.

Conclusions: The acute and chronic toxicity profiles associated with these 3 HDR brachytherapy schedules were similar and were well tolerated. Acceptable grade 2, minimal grade 3, and no grade 4 or 5 toxicities were seen. This, combined with the fact that the clinical outcomes were similar, leads to the conclusion that all 3 regimens may be acceptable options for the management of low-risk to intermediate-risk prostate cancer.