Pre-operative assessment of extramural invasion and sphincteral involvement in rectal cancer by magnetic resonance imaging with phased-array coil

Objective: Pre-operative staging of rectal cancer should identify patients with extrarectal spread, who might benefit from pre-operative radiotherapy, and patients with minimal sphincteral involvement, who can avoid permanent colostomy. The aim of this study was to assess the accuracy of Magnetic Resonance Imaging (MRI) to predict turnout stage and sphincter status. Patients and methods: Thirty-three patients with a rectal tumour were pre-operatively assessed by MRI with a phased-array coil. Imaging results were correlated with the final pathological findings. Results: The overall accuracy of pre-operative staging with MRI was 88% (k = 0.75) for extramural tumour invasion and 59% (k = 0.26) for lymph node metastases. MRI correctly evaluated the infiltration of the anal sphincters in 87% of patients (7 of 8 patients with low rectal tumour). Conclusion: MRI provides the surgeon with valuable information regarding extramural tumour spread and sphincteral involvement, enabling appropiate selection of patients for pre-operative adjuvant therapy or sphincter-saving sugery.