Patient and physician reported toxicity with two-fraction definitive high-dose-rate prostate brachytherapy: the impact of implant interval

Introduction
High-dose-rate (HDR) brachytherapy is an effective method of treating localized prostate cancer. There are limited data on the relationship between implant interval and outcomes. This study aims to assess if the implant interval between HDR treatments has an impact on patient-reported health-related quality of life (QOL) and physician-graded toxicity in men treated for localized prostate cancer.

Material and methods
Patients were treated with HDR brachytherapy as monotherapy with 27 Gy in 2 fractions, given over two implants, performed 1-2 weeks apart. Patients were dichotomized into one-week and two-week cohorts. Patient-reported EPIC-26 genitourinary (GU), gastrointestinal (GI), and sexual QOL were assessed. Linear regression, chi-squared testing, and generalized linear mixed effect models were used to assess the differences in patient characteristics, patient-reported QOL, and physician-graded toxicity.

Results
Outcomes of 122 patients were analyzed. Median follow-up was 18 months. Patient-reported GU and GI QOL worsened after treatment with a return towards baseline over time, while patient-reported sexual QOL worsened after treatment, but did not return towards baseline. There were no differences in patient-reported health related QOL as a function of implant interval. Maximum physician-graded GU, GI, and sexual toxicity rates of grade 2 or 3 were 68%, 3%, and 53%, respectively. There was no difference in rates of grade 2 or 3 toxicity as a function of implants interval.

Conclusions
HDR brachytherapy for prostate cancer is a well-tolerated treatment. The interval between treatments is not associated with differences in patient-reported QOL or physician-graded toxicities.