Magnetic Resonance Imaging In Restaging Rectal Cancer After Neoadjuvant Chemoradiotherapy

PurposeTo evaluate the accuracy of magnetic resonance imaging (MRI) for restaging locally advanced nonmucinous rectal cancer after neoadjuvant chemoradiotherapy (N-CRT).Materials and MethodsA total of94consecutive patients with histologically proven locally advanced middle or low located nonmucinous rectal adenocarcinoma, who were treated with preoperative CRT, followed by radical surgery6-8weeks later, were analyzed in this retrospective study. Pre-CRTand post-CRT MR images were interpreted by one radiology expert and the results were compared with the histologic findings. The overall MRI tumor (T) and nodal (N) restaging accuracy were calculated. The agreement between post-CRT MRI examination and histological assessment was evaluated by using kappa statistics. ResultsThe overall accuracy of MRI for T restaging was49%, with overstaging and understaging occurring in40.4%and10.6%of the patients, respectively. Only18%of the patients with pathological complete response (pCR) were staged correctly by MRI, nevertheless an excellent100%specificity in predicting pCR was detected. For N restaging with MRI, the overall accuracy was63.8%, whereas26.6%of the patients were overstaged and9.6%were understaged. Kappa statistics revealed poor concordance of MRI restaging after preoperative CRT and pathological results in both T (k=0.156) and N staging (k=0.289).ConclusionsThe accuracy of MRI for restaging rectal cancer is at a low level. Restaging rectal cancer still remains a challenge and better methods are urgently required. We suggest that the surgical plan before treatment should not be changed except in those cases who had pCR, intolerance or refusing radical operation, for whom an observation strategy could be taken into consideration after the excellent specificity in predicting pCR..