Late toxicity after single dose HDR prostate brachytherapy and EBRT for localized prostate cancer: Clinical and dosimetric predictors in a prospective cohort study

Abstract Purpose To describe the genitourinary (GU) and gastrointestinal (GI) late toxicity profile and to analyse the clinical and dosimetry outcomes predictors of the combination of EBRT and high-dose-rate (HDR) prostate brachytherapy (BT) for localized prostate cancer. Materials and methods Between January 2012 and May 2017, 210 patients were included in a prospective protocol. Treatment consisted in HDR-BT (15 Gy single fraction) plus 3DCRT (37.5 Gy/15 fractions). Univariate and multivariate logistic regressions were used to analyse the impact of variables on late toxicity. Results Median age was 71 (56–82), 12.4% of patients had low, 44.3% intermediate and 41% high-risk prostate cancer. Median prostate volume was 28.4 cc. Median V100, V150, V200 were 98.2%, 27% and 7.4% respectively. Median urethra Dmax, rectum D1cc and D2cc, were 113.5%, 62.2%% and 54.2% respectively. After a median follow-up of 41 months (5–75) late G2 GU and GI late toxicity was observed in 14.8% and 5.2% of patients respectively. Late G3 GU and GI toxicity occurred in 0% and 1% of patients respectively. There were no outcome correlations with late G  ≥ 2 GU toxicity on univariate analysis. Previous cardiovascular comorbidity ( p  = 0.042), and dose to the rectum D2cc ( p  = 0.016) and D1cc ( p  = 0.017) were associated with G  ≥ 2 GI toxicity. Multivariate analysis showed that rectum D1cc (HR11.56; 95%CI 1.4–92.1; p  = 0.021) and prior history of cardiovascular disease (HR3.6; 95%CI 1–12.9; p  = 0.045) remained independent predictors of G  ≥ 2 GI toxicity. Conclusions There is a low incidence of late GU and GI morbidity using single fraction HDR-BT and hypofractionated EBRT. Previous cardiovascular disease and dose to the rectum were observed to correlate with GI toxicity.