High-dose-rate brachytherapy boost for prostate cancer: Outcomes and genitourinary toxicity.

AIMS: To report disease outcomes and late urinary toxicity profile. To assess the impact of changing technique and evolving quality assurance on genitourinary toxicity rates.

METHODS AND MATERIALS: One hundred eighty patients were treated with external beam radiation therapy and high-dose-rate brachytherapy (HDRB) for localized intermediate- and high-risk prostate cancer, between December 2002 and February 2012. The HDRB technique evolved over the period of this study, from 19.5 Gy/3 (n = 68), to 17 Gy/2 (n = 40), 18 Gy/2 (n = 39), and most recently 19 Gy/2 (n = 33). In the two fraction cohort, 68 patients underwent additional correction for catheter displacement before each fraction.

RESULTS: With a median followup of 5.2 years, 5-year freedom from failure was 93.7% for intermediate, and 76.0% for high risk patients. The 3- and 6-year cumulative stricture incidence for all patients was 7.8% and 15.3%, respectively. There was no statistically significant difference in stricture rate for the four dose levels used nor between the three fractions and the two fraction technique overall. The 19 Gy/2 fractionation group had the lowest 3-year stricture rate (3.0%). The addition of correction for intrafraction catheter displacement did not result in a statistically significant difference in stricture rates, although the severity of strictures has been reduced.

CONCLUSIONS: Our biochemical control is consistent with other similar series. We found no increase in late urinary toxicity with a two fraction, two implant HDRB technique compared with three fractions. The HDRB dose did not correlate with stricture rates in our series. Correction of intra-fraction catheter displacement did not lead to a statistically significant reduction in stricture rates, although may have mitigated the effects of dose escalation.