Combined brachytherapy and ultra-hypofractionated radiotherapy for intermediate-risk prostate cancer: Comparison of toxicity outcomes using a high-dose-rate (HDR) versus low-dose-rate (LDR) brachytherapy boost

PURPOSE/OBJECTIVE: To compare toxicity profiles of low-dose rate (LDR) and high-dose rate (HDR) brachytherapy boost combined with ultra-hypofractionated external beam radiation therapy (UH-EBRT). MATERIALS/METHODS: 99 patients with intermediate-risk prostate cancer underwent an HDR ( n = 59) or LDR ( n = 40) boost combined with UH-EBRT (5 Gy x 5) . HDR (Ir-192) was delivered a single dose (15 Gy) and LDR (Pd-103) prescription dose was 100 Gy. Median baseline IPSS was 5 for both cohorts. Median follow-up was 29.3mos. Cumulative incidences were calculated for toxicity. Fisher exact tests were used to evaluate associations. RESULTS: Overall incidence of grade 2 genitourinary toxicity for the entire cohort at 12 and 24 months was 21% and 29%, respectively. The incidence of grade 2 genitourinary toxicity at 12 and 24 months was higher for LDR cohort compared with HDR cohort (45% vs 5.1% and 55% vs 11%; p < 0.001). On MVA, only treatment regimen (LDR versus HDR) was associated with grade 2+ genitourinary toxicity ( p < 0.001). Two patients experienced grade 2 rectal toxicity in each cohort. No grade > 3 toxicities were observed. CONCLUSIONS: Both LDR and HDR brachytherapy combined with UH-EBRT had favorable toxicity profiles, but significantly less grade 2 + genitourinary toxicity was observed in patients receiving HDR. (C) 2022 American Brachytherapy Society. Published by Elsevier Inc. All rights reserved.