OBJECTIVETo evaluate the application value of magnetic resonance diffusion-weighted imaging (DWI) combined with routine T2WI sequence in the determination of pathological complete response (pCR) after neoadjuvant therapy for rectal cancer.

METHODSClinical data of 51 cases with locally advanced mid-low rectal cancer undergoing neoadjuvant therapy plus radical resection in the Rectal Cancer Center at The Sixth Affiliated Hospital of Sun Yat-sen University from June 2012 to April 2013 were analyzed retrospectively. Magnetic resonance DWI and T2WI sequences scanning were performed within 1 week before neoadjuvant therapy and within 1 week before operation. Routine single T2WI sequence and DWI combined with T2WI sequence were used separately to predict the residual tumor and to compare with postoperative pathological examination. The prediction values of two methods were compared.

RESULTSOf 51 patients, 12 cases had pathological complete response (pCR). Prediction of DWI combined T2WI sequence was correct in 8 cases of pCR, whose sensitivity and specificity were higher than those of routine single T2WI sequence (66.7%, 94.9% vs. 33.3%, 84.6%). Prediction value of DWI combined T2WI sequence for pCR was significantly higher as compared to routine single T2WI sequence (AUC, 0.808 vs. 0.590, P=0.001).

CONCLUSIONCompared with the routine single T2WI sequence, DWI combined with T2WI sequence can improve the prediction accuracy of pathological complete response.