Diagnostic accuracy and prognostic impact of restaging by magnetic resonance imaging after preoperative chemoradiotherapy in patients with rectal cancer.

Background: The prognostic role of restaging rectal magnetic resonance imaging (MRI) in patients with preoperative CRT has not been established. The goal of this study was to evaluate the diagnostic accuracy and prognostic role of radiological staging by rectal MRI after preoperative chemoradiation (CRT) in patients with rectal cancer.

Methods: A total of 231 consecutive patients with rectal cancer who underwent preoperative CRT and radical resection from January 2008 to December 2009 were prospectively enrolled. The diagnostic accuracy and prognostic significance of post-CRT radiological staging by MRI was evaluated.

Results: The sensitivity, specificity, positive predictive value, and negative predictive value of radiological diagnosis of good responders (ypTNM stage 0-I) were 32%, 90%, 65%, and 69%, respectively. The overall accuracy of MRI restating for good responders was 68%. The 5-year disease-free survival rates of patients with radiological and pathological TNM stage 0, stage I, and stage II-III were 100%, 94%, and 76%, respectively (P=0.037), and 97%, 87%, and 73%, respectively (P=0.007). On multivariate analysis, post-CRT radiological staging by MRI was an independent prognostic factor for disease-free survival.

Conclusion: Radiological staging by MRI after preoperative CRT may be an independent predictor of survival in patients with rectal cancer.