Single 15 Gy High-Dose-Rate Brachytherapy Boost for Treatment of Prostate Cancer: Long-Term Results of Changes in Health-Related Quality of Life and Toxicity

Abstract

To report long-term changes in health-related quality of life and toxicity in prostate cancer patients treated with single 15 Gy high-dose-rate brachytherapy and hypofractionated external beam radiotherapy and also to investigate the relationship between these changes and baseline clinical and dosimetric factors. The study accrued 125 patients with intermediate-risk prostate cancer. They received a single 15 Gy high-dose-rate brachytherapy followed by external beam radiotherapy to 37.5 Gy in 15 fractions. Health-related quality of life (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, version 3.0) were monitored prospectively. Univariate and multivariate logistic regression analysis was used to investigate associations between health related quality of life/toxicity and baseline covariates. Median followup time was 5.1 years. The change in the median EPIC scores from baseline to year 5 in urinary domain was from 91 to 85 (p = 0.0015), in bowel domain was from 98 to 96 (p = 0.04), in sexual domain was from 63 to 31 (p < 0.0001), and hormonal domain remained unchanged at 95 (p = 0.69). Median IPSS changed from 5 at baseline to 12 at 1 month, but returned to within 2 points of baseline by month 3, and remained 1-3 points higher than baseline up to year 5. Median IIEF score dropped from 19 at baseline to 6 at 12 months and remained unchanged up to year 5 (p < 0.0001). At year 5, the proportion of patients experiencing grade 1, 2, and 3 or higher urinary frequency was 50%, 5% and 0%, and for urinary incontinence was 19%, 5% and 0%, respectively. With regards to GI toxicity at year 5, the proportion of patients with grade 1, 2, and 3 or higher proctitis was 0%, 1.5%, and 0% and for rectal bleeding was 1%, 0%, and 0%, respectively. On multivariate analysis, patients with higher prostate volume were more likely to develop a urinary late toxicity grade 2 or more (p = 0.0036). On multivariate analysis, the dose to 10% of the urethra was the only factor associated with a decreasing EPIC urinary domain score (p = 0.012). Patients with higher baseline IIEF score are more likely to have clinically significant decrement in sexual domain (OR = 1.06; p = 0.013). Single fraction 15 Gy high-dose-rate brachytherapy with hypofractionated external beam radiotherapy has a low rate of late GU and GI toxicities. Late urinary morbidity may be minimized by limiting dose to urethra, particularly for patients with larger prostates.