Association of urethral toxicity with dose exposure in combined high-dose-rate brachytherapy and intensity-modulated radiation therapy in intermediate- and high-risk prostate cancer

Abstract Introduction To report acute and late toxicities in patients with intermediate- and high-risk prostate cancer treated with combined high-dose-rate brachytherapy (HDR-B) and intensity-modulated radiation therapy (IMRT). Materials and methods From March 2003 to September 2005, 64 men were treated with a single implant HDR-B with 21Gy given in three fractions, followed by 50Gy IMRT along with organ tracking. Median age was 66.1 years, and risk of recurrence was intermediate in 47% of the patients or high in 53% of the patients. Androgen deprivation therapy was received by 69% of the patients. Toxicity was scored according to the CTCAE version 3.0. Median follow-up was 3.1 years. Results Acute grade 3 genitourinary (GU) toxicity was observed in 7.8% of the patients, and late grades 3 and 4GU toxicity was observed in 10.9% and 1.6% of the patients. Acute grade 3 gastrointestinal (GI) toxicity was experienced by 1.6% of the patients, and late grade 3GI toxicity was absent. The urethral V 120 (urethral volume receiving ⩾120% of the prescribed HDR-B dose) was associated with acute ( P =.047) and late⩾grade 2GU toxicities ( P =.049). Conclusions Late grades 3 and 4GU toxicity occurred in 10.9% and 1.6% of the patients after HDR-B followed by IMRT in association with the irradiated urethral volume. The impact of V 120 on GU toxicity should be validated in further studies.