High-dose-rate interstitial brachytherapy as monotherapy in one fraction of 20.5 Gy for the treatment of localized prostate cancer: Toxicity and 6-year biochemical results.

PURPOSE: To evaluate acute and late genitourinary toxicity, the gastrointestinal toxicity, and the long-term biochemical control after high-dose-rate (HDR) monotherapy in one fraction (20.5 Gy). MATERIALS AND METHODS: Between May 2011 and October 2014, 60 consecutive patients with low- and intermediate-risk prostate cancer were treated; the median followup was 51 months (range 30-79). All patients received one implant and one fraction of 20.5 Gy HDR real-time U/S planned with transperineal hyaluronic acid injection into the perirectal. Toxicity was reported according to the Common Toxicity Criteria for Adverse Event, Version 4.0 (CTAE v4.03) by the National Cancer Institute. Biochemical failure was defined according to the "Phoenix definition". RESULTS: Our experience in a single fraction of 20.5 Gy HDR brachytherapy is well-tolerated. No intraoperative or perioperative complications occurred. Grade 1 acute genitourinary toxicity occurred in 36% of patients, Grade 2 or more was not observed, only 1 patient requiring the use of a catheter for 7 days in the immediate postoperative period. No gastrointestinal toxicity was observed. No chronic toxicity has been observed after treatment. Morbidity is practically the same as that obtained with 19 Gy in our previously published article but the actuarial biochemical control was better, 82% (±3%) at 6 years. CONCLUSIONS: A single dose of 20.5 Gy resulted in a low genitourinary morbidity and no gastrointestinal toxicity and achieves good levels of biochemical disease control.