OBJECTIVETo assess the correlation of preoperative high-resolution-MRI with histopathologic findings in tumor staging of rectal carcinoma.

METHODSFrom January 2005 to December 2008, 245 cases of pathologically confirmed rectal cancer, who received preoperative scan by a 1.5 T high-resolution-MRI were included in this retrospective study. To extract image signs from high-resolution MRI, and made a diagnosis for tumor staging classification. Assessment for diagnostic accuracy of high-resolution MRI was extract made with comparison of histopathological classification.

RESULTSThe overall diagnostic accuracy of T-stage was 83.7% (205/245). The consistency coefficient (κ) between the MRI and histopathologic T-stage was 0.693 (95%CI: 0.611 - 0.776), which was considered good. For the 97 cases with preoperative chemoradiotherapy, the agreement rate between the post-chemoradiotherapy MRI and histopathologic T-stage was 73.2% (71/97, κ = 0.563, 95%CI: 0.428 - 0.698). For the 148 cases without preoperative chemoradiotherapy, the agreement rate between the MRI and histopathologic T-stage was 90.5% (134/148, κ = 0.794, 95%CI: 0.692 - 0.896). The histopathologic T-stage and diameter infringement were in moderate related degree (ρ = 0.619, P < 0.01).

CONCLUSIONSHigh-resolution MRI is proved to have a high degree of diagnostic accuracy for T-stage of rectal carcinoma. Preoperative MRI is helpful in treatment planning. Patients undergoing preoperative chemoradiotherapy should receive MRI scan again after neoadjuvant therapy for restaging. The assessment of circumference violation make sense for the accurate diagnosis for tumor staging.