To report health-related quality of life (HRQOL) and toxicity in prostate cancer patients treated with single-fraction high dose rate (HDR) brachytherapy boost and external beam radiotherapy (EBRT).

Patients with intermediate-risk prostate cancer were accrued to a phase II clinical trial of 15 Gy HDR boost and EBRT to a dose of 37.5 Gy in 15 fractions. HRQOL (Expanded Prostate Cancer Index Composite [EPIC]), urinary symptoms (International Prostate Symptom Score [IPSS]), erectile function (International Index of Erectile Function [IIEF]) and toxicity (Common Terminology Criteria for Adverse Events [CTCAE], version 3.0) were monitored prospectively. Univariate and multivariate logistic regression analysis was used to investigate associations between HRQOL/toxicity and baseline covariates.

The median follow-up time was 5.2 years. The change in the median EPIC scores from baseline to year 5 in the urinary domain was from 91 to 85 (P = 0.0028), in the bowel domain was from 98 to 96 (P = 0.03), in the sexual domain was from 63 to 35 (P < 0.0001) and the hormonal domain remained unchanged at 95 (P = 0.93). Fifty-nine per cent and 46% of the patients with normal erectile function at baseline remained potent at year 1 and year 5, respectively. Late genitourinary toxicity grade 1, 2 and ≥3 occurred in 29, 59 and 4% of patients, respectively. The rates of late gastrointestinal toxicity grade 1, 2 and ≥3 were documented as 45, 19 and 0%, respectively. On multivariate logistic regression analysis, patients with larger prostates were more likely to develop a urinary late toxicity grade ≥2 (P = 0.01). The dose to 10% of the urethra was the only factor associated with a decline in the EPIC urinary domain score (P = 0.012). Prostate volume >43 ml was associated with higher late genitourinary toxicity grade ≥2.

Single 15 Gy HDR brachytherapy with EBRT has a low rate of late genitourinary and gastrointestinal toxicities. Late urinary morbidity may be minimised by limiting the dose to the urethra, particularly for patients with larger prostates.