To examine late gastrointestinal (GI) and genitourinary (GU) toxicity profiles of patients treated for prostate cancer either definitively or post-prostatectomy with both intensity modulated radiation therapy (IMRT) and image guided radiation therapy (IGRT).

A total of 333 patients treated definitively and 104 patients treated postoperatively with IMRT and varying IGRT techniques were retrospectively examined to evaluate GI and GU toxicity profiles >1 year from treatment. Available dosimetric data were used for correlative analysis.

The median follow-up time for the definitive patients was 41 months and the median follow-up time for the post-prostatectomy patients was 33 months. No late grade 4 or 5 GI or GU toxicities were observed. For definitive patients, the rates of grade ≥2 GI and GU toxicity at 3 years were 4.9% and 4.5%, respectively. In the postoperative cohort the rate of grade >2 GU toxicity was 11.6%, with no grade ≥2 GI toxicity. In the definitive cohort's Cox proportional hazards regression univariate analysis, use of anticoagulation was significantly associated with GI toxicity and age, bladder V50 and IGRT modality were associated with GU toxicity, and only age remained significant in the multivariate model. In univariate analysis for the postoperative cohort, no dosimetric value correlated with GU toxicity, nor did age or time from radical prostatectomy to radiation.

IMRT with IGRT achieved low rates of GI and GU toxicity in the definitive and postoperative setting.