Acute toxicity with intensity modulated radiotherapy versus 3-dimensional conformal radiotherapy during preoperative chemoradiation for locally advanced rectal cancer.

BACKGROUND AND PURPOSE: We examined acute toxicity profiles and outcomes among rectal cancer patients treated with pre-operative chemoradiation using intensity modulated radiotherapy (IMRT) or 3-dimensional conformal radiotherapy (3DCRT) to identify predictive clinical factors associated with increased acute toxicity.

MATERIAL AND METHODS: We retrospectively reviewed records of 301 consecutive rectal cancer patients treated with pre-operative chemotherapy and radiotherapy (median dose 5000cGy) at our institution between 2007 and 2014.

RESULTS: Of the 301 patients, 203 (67.4%) were treated with IMRT and 98 (32.6%) with 3DCRT. Significantly more patients experienced ⩾grade 2 diarrhea in the 3DCRT group compared to the IMRT group (22% vs 10%, p=0.004), and those who received 3DCRT had 2.7 times greater odds of a higher diarrhea score than those on IMRT, even after adjusting for patient characteristics and chemotherapy (OR 2.71, p=0.01) Fewer patients experienced grade 2 genitourinary toxicity in the IMRT group (6% vs 13% 3DCRT, p=0.04) and there was a trend toward decreased grade 2 proctitis in the IMRT group (22% vs 32% 3DCRT, p=0.07). Patients over the age of 55 had 45% lower odds of proctitis than patients younger than 55.

CONCLUSION: The use of IMRT significantly reduced grade ⩾2 diarrhea and GU toxicity during chemoradiation. Younger patients were more likely to report grade 2 or higher proctitis.