Comparison of outcomes of intensity-modulated radiotherapy and 3-D conformal radiotherapy for anal squamous cell carcinoma using a propensity score analysis.

3555 Background: IMRT has been shown to reduce acute dermatologic and gastrointestinal toxicities when compared to 3DCRT in the treatment of ASCC; however, there has been concern that focal IMRT fields may lead to elevated rates of locoregional recurrence. We examined the efficacy of definitive chemoradiation (CRT) using intensity modulated radiotherapy (IMRT) as compared with 3D conformal radiotherapy (3DCRT) for patients (pts) with anal squamous cell carcinoma (ASCC). Methods: We retrospectively assessed 221 pts with ASCC treated with definitive CRT at MSKCC from 05/1991 to 01/2010. Of these pts, 44 received IMRT between 07/2005-01/2010, and 177 received 3DCRT between 05/1991-04/2007. Local recurrence-free survival (LRFS), distant metastasis-free survival (DMFS), colostomy-free survival (CFS), and overall survival (OS) were estimated by Kaplan-Meier methods and compared using a log-rank test. To account for biases arising from nonrandom allocation of pts to treatment groups, a propensity score analysis ...