Abstract
PURPOSE: Androgen deprivation therapy (AD) has been shown to increase late ≥ grade 2 rectal toxicity when used concurrently with three-dimensional conformal radiotherapy (3DCRT). Intensity modulated radiotherapy (IMRT) has the potential to reduce toxicity by limiting the radiation dose received by the bowel and bladder. This study compares both genitourinary (GU) and gastrointestinal (GI) toxicity in men treated with 3DCRT+AD versus IMRT+AD. METHODS AND MATERIALS: From July 1992 to July 2004, 293 men received 3DCRT (n=170) or IMRT (n=123) with concurrent AD (< 6 months, n=123; ≥ 6 months, n =170). Median RT doses were 76 Gy for 3DCRT (ICRU) and 76 Gy for IMRT (95% to the PTV). Toxicity was assessed by a patient symptom questionnaire assessing toxicity completed at each visit and recorded using a modified late effects normal tissue task force radiation morbidity scale (LENT). RESULTS: Mean follow-up was 86 months (SD=29.3) for the 3DCRT group and 40 months (SD=9.7) for the IMRT group. Acute GI toxicity (OR=4, 95% CI: 1.6-11.7, p=0.005) was significantly higher with 3DCRT than with IMRT and was independent of AD duration (i.e. <6 vs. ≥6 months). Time to development of late GI toxicity was significantly longer in the IMRT group. The 5-year Kaplan-Meier estimates for ≥ grade 2 GI toxicity were 20% for 3DCRT versus 8% for IMRT (p=0.01). On MVA, ≥ grade 2 late GI toxicity (HR=2.1, 95% CI: 1.1-4.3, p=0.04) was more prevalent in 3DCRT patients. CONCLUSIONS: Compared to 3DCRT, IMRT significantly decreased acute and late GI toxicity in patients treated with AD.