Focal or whole-gland salvage prostate brachytherapy with iodine seeds with or without a rectal spacer for postradiotherapy local failure: How best to spare the rectum?

PURPOSE: Salvage prostate permanent implant (sPPI) for postradiation local failure provides high rates of biochemical control. The cumulative dose delivered to the prostate and the rectum is still unknown. METHODS AND MATERIALS: We reviewed the postimplant CT-based dosimetry of 18 selected patients who underwent sPPI with I-125 seeds for isolated biopsy-proven local failure several years after external beam radiation therapy. Ten patients had whole-prostate sPPI, and 8 patients had multiparametric MRI-based focal sPPI. In 8 patients, hyaluronic acid (HA) gel was injected into the prostate rectum space. RESULTS: The median cumulative biological effective dose after EBRT sPPI for the prostate and the rectum was higher in patients treated with whole-gland sPPI than in patients treated with focal sPPI (313.5 Gy(2) vs. 174.4 Gy(2); p = 0.06 and 258.1 Gy(3) vs. 172.6 (Gy3); p < 0.01, respectively). The median Dolcc for the rectum was significantly lower in patients who had HA gel: 63.3 Gy (29.0-78.3) vs. 83.9 Gy (34.9-180.0) (p = 0.04). CONCLUSIONS: Cumulative prostate and rectum biological effective doses were lower with focal sPPI. Duce delivered to the rectum was significantly lower with HA gel, while there was no difference between focal or whole-gland plans. (C) 2016 American Brachytherapy Society. Published by Elsevier Inc. All rights reserved.