Rectal cancer: Assessment of response to neoadjuvant chemoradiation by dynamic contrast-enhanced MRI

Purpose To assess pretreatment functional and morphological tumor characteristics with magnetic resonance imaging (MRI) in advanced rectal carcinoma and to identify factors predicting response to neoadjuvant chemoradiation. Materials and Methods In a prospective study, 95 patients with rectal carcinoma underwent dynamic contrast‐enhanced MRI before and after chemoradiation. Quantitative parameters were derived from a pharmacokinetic two‐compartment model. Tumors were also characterized with regard to mucinous status at pretreatment high‐resolution MRI as nonmucinous or mucinous. Response to treatment was defined as a downshift in the local tumor stage. Results The parameter k21 (contrast medium exchange rate) was higher at pretreatment MRI in nonmucinous compared with mucinous carcinomas (P < 0.001). The effect of chemoradiation on dynamic MR parameters was higher in nonmucinous carcinomas than in the mucinous subtype (P < 0.001). A higher rate of response to treatment was linked with nonmucinous morphology (P < 0.001). Multivariate analysis revealed an association between mucinous tumor morphology and poor response (odds ratio [95% confidence interval]: 0.113 [0.032–0.395], P < 0.001) as well as an association between a high 75th percentile of k21 and a higher response rate (odds ratio: 1.043 [1.001–1.086], P = 0.019). Conclusion Functional and morphological parameters of pretreatment MRI can assess tumor characteristics associated with the effectiveness of chemoradiation before treatment initiation. J. Magn. Reson. Imaging 2013;38:119–126. © 2012 Wiley Periodicals, Inc.