High dose rate brachytherapy for prostate cancer: A prospective toxicity evaluation of a one day schedule including two 13.5 Gy fractions

High dose-rate (HDR) brachytherapy (BT) provides a highly conformal method of dose delivery to the prostate. The purpose of this study is to prospectively determine the toxicity of the treatment protocol of 13.5 Gy × 2 fractions. From 2010 through 2017, 119 patients with low (71%) or intermediate-risk prostate cancer were prospectively treated in a single institute with HDR-BT at 13.5 Gy × 2 fractions within one day. Median follow-up time was 4.4 years. Actuarial rates of no biochemical evidence of disease, overall survival and metastasis-free survival for all patients were 96%,98% and 98%, respectively. The cumulative incidence of acute grade 2 and 3 genitourinary (GU) toxicity was 9% and 2%, respectively. The corresponding incidences of late GU toxicity were 18% and 1%. No grade ≥4 of either type of toxicity was detected. Multivariate analysis showed that having higher international prostate symptom score (IPSS; P = 0.041) or higher V200 (P = 0.013) was associated with a higher risk of experiencing any grade of acute GU toxicity. In addition, patients having a higher IPSS (P = 0.019) or a higher V150 (P = 0.033) were associated with a higher grade >1 acute GU toxicity. The findings of this study show that HDR-BT 13.5 Gy × 2 as monotherapy was safe and effective for prostate cancer patients with low-intermediate risk.