Dynamic contrast-enhanced MRI: Use in predicting pathological complete response to neoadjuvant chemoradiation in locally advanced rectal cancer.

PurposeTo determine the ability of dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI) to predict pathological complete response (pCR) before preoperative chemoradiotherapy (CRT) in locally advanced rectal cancer. Materials and MethodsIn a prospective clinical trial, 38 enrolled patients underwent pre- and post-CRT DCE-MRI at 3.0T. The tumor length and the following perfusion parameters (K-trans, k(ep), v(e)) were measured for the tumor and compared between the pCR group and the non-pCR group, as well as before and after CRT. For categorical variable comparison, the Kruskal-Wallis test was used. P<0.05 was considered significant. ResultsNo difference in tumor length was found between the pCR and non-pCR group pre- and post-CRT (P=0.26 (0.15,0.45), 0.35 (0.21,0.52), respectively). Before CRT, the mean tumor K-trans in the pCR group was significantly higher than in the non-pCR group (P=0.01). A K-trans of 0.66 emerged as the best cutoff for distinguishing pCR from non-pCR. Regarding k(ep) and v(e), significant differences were also observed between the pCR and non-pCR groups (P=0.02, 0.01, respectively). The mean K-trans, k(ep), and v(e) values post-CRT were lower in the pCR group than in the non-pCR group, although there was no significant difference (P=0.10 (0.04,0.16), 0.11 (0.07,0.26), 0.10 (0.06,0.23), respectively). ConclusionBefore neoadjuvant chemoradiotherapy in rectal cancer, DCE-MRI can distinguish between complete and incomplete response using a K-trans threshold of 0.66 with a sensitivity of 100%. J. Magn. Reson. Imaging 2015;42:673-680.