Diffusion-weighted magnetic resonance imaging for. monitoring diffusion changes in rectal carcinoma during combined, preoperative chemoradiation: preliminary results of a prospective study

Purpose: To evaluate the clinical value of diffusion-weighted magnetic resonance imaging (DW-MRI) to monitor response of primary carcinoma of the rectum to preoperative chemoradiation by measuring tumor apparent diffusion coefficient (ADC). Materials and methods: Diffusion data of nine patients undergoing preoperative combined chemoradiation for clinical staged T3, N0-2, M-0 carcinoma of the rectum were analyzed. Diffusion-weighted echo-planar MR images were obtained prior to and at specified intervals during chemoradiation and ADCs calculated from acquired tumor images. Results: Comparison of mean ADC and cumulative radiation dose showed a significant decrease of mean ADC at the 2nd (P = 0.028), 3rd (P = 0.012), and 4th (P = 0.008) weeks of treatment. Cytotoxic edema and fibrosis were considered as reasons for ADC decrease. Conclusion: This study demonstrated tumor ADC changes via detection of therapy-induced alterations in tumor water mobility. Our results indicate that diffusion-weighted imaging may be a valuable clinical tool to diagnose the early stage of radiation-induced fibrosis. (C) 2002 Elsevier Science Ireland Ltd. All rights reserved.