Value of dynamic contrast-enhanced MRI in predicting response to neoadjuvant chemoradiation in locally advanced rectal cancer

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Objective To determine the value of dynamic contrast enhanced (DCE- MRI) in predicting treatment response before preoperative chemoradiotherapy in locally advanced rectal cancer. Methods A cohort of consecutive patients with histologically confirmed rectal adenocarcinoma treated with preoperative chemoradiotherapy followed by total mesorectal excision (TME) surgery was enrolled in a prospective, pilot trial. All enrolled patients were examined using DCE-MRI at two time points: 2 to 5 days before neoadjuvant chemoradiation, 1 to 4 days before surgery. The following perfusion parameters (Ktrans, Kep, Ve) were measured for tumor. The patients were classified into pathological complete response (pCR) and non -pCR group according to the pathological results after operation. Those perfusion parameters were compared between the pCR and the non-pCR group and between before and after CRT in pCR and the non-pCR group with thet test. Receiver-operating curves (ROC) were constructed to further investigate the predictive value of Ktrans, Kep, Ve before neoadjuvant chemoradiation and were used to determine a threshold value at which patents with pCR could be distinguished from patients without complete response. Results The final study population consisted of 38 patients. There were 12 patients with a pCR and 26 patients with non-pCR. Before neoadjuvant chemoradiation, the mean tumor Ktrans, Kep and Ve for pCR group were (1.25±0.56)/min, (2.10±1.61)/min and 0.73±0.34, respectively, for non-pCR group they were (0.46±0.39)/min, (1.15±0.77)/min and 0.32±0.12, respectively. All perfusion parameters showed significant difference between those two groups (t values were 3.45,5.67 and 6.23 respectively, allP 0.05), as well as the changes before and after neoadjuvant chemoradiation in those groups (P>0.05) . ROC analysis for Ktrans pre-treatment revealed that Ktrans had an AUC of 0.837 in predicting pCR. A Ktrans of 0.66/min was emerged as the optimal cut- off for distinguishing pCR from non- pCR and for Ktrans>0.66/min, the sensitivity and specificity for predicting pCR were 75.0% (9/12) and 96.2% (25/26). Kep and Ve showed an AUC of 0.655 and 0.654 in predicting pCR. Conclusions In locally advanced rectal cancer, DCE-MRI can aid in predicting treatment response before preoperative chemoradiotherapy. Ktrans may become a better predictor to classify which patients will benefit from neoadjuvant chemoradiation. Key words: Rectal neoplasms; Magnetic resonance imaging; Comparative study