Toxicity of hypofractionated intensity-modulated radiotherapy in patients with prostate cancer

Objective: To analyze the acute and late toxicities in patients with prostate cancer trea- ted with hypofractionated intensity-modulated radiotherapy (IMRT). Methods: Between June 2006 and June 2008, 37 patients with prostate cancer were treated with hypofractionated IMRT. The clinical target volume (CTV) was the prostate, seminal vesicles and pelvic lymph nodes in 24 patients, the prostate and seminal vesicles in 12, and only the tumor' bed in 1. The dose per fraction was 2.3-2.8 Gy, with 2.7 Gy in 26 patients. The minimal dose was 62.5-75.0 Gy to the prostate and seminal vesicles, and 50 Gy to the pelvic lymph nodes. Results: The median follow-up was 14 months. None of the patients experienced grade 4 a- cute gastro-intestinal (GI) toxicity. Grade 1, 2 and 3 acute GI toxicity occurred in 24.3% , 35.1% and 2.7% of the patients, respectively. The rectal V50 > 27% and V55 > 20% were highly significantly associated with grade ≥1 acute GI toxicity. Grade 1, 2 and 3 acute genitourinary (GU) toxicity occurred in 68%, 0% and 3% of the patients, respectively. The bladder V60 > 10% was significantly associated with grade ≥ 1 acute GU toxicity. The incidence of late GI toxicity was low. No grade ≥3 late GI toxicity was observed. The incidence of late grade 1 and 2 GI toxicity was 24% and 5%, respectively. The rectal V65>10% was highly significantly associated with grade ≥1 late GI toxicity. No late grade 4 GU toxicity was observed. The incidence of grade 1, 2 and 3 late GU toxicity was 49%, 11% and 3%, respectively. Grade ≥2 late GU toxicity was correlated with V40, V50 and mean dose of the bladder. Conclusions: Acute and late toxicity of hypofractionated IMRT is acceptable in patients with prostate cancer. (authors)