The ability of phased-array MRI in preoperative staging of primary rectal cancer: correlation with histopathological results.

PURPOSE: This study evaluated the accuracy of phased-array magnetic resonance imaging (MRI) for preoperative local tumor staging in primary rectal cancer and emphasized the importance of the preoperative differentiation of T2 tumors from T3 tumors so the appropriate treatment can be applied. MATERIALS AND METHODS: Twenty-four patients with primary rectal cancer were examined preoperatively using 1.5 T MRI with a phased-array coil. Multiplanar T2-weighted images were obtained. Rectum anatomy, depth of tumor invasion, mesorectal involvement and lymph nodes were assessed. All patients underwent radical surgery. The histological sections were evaluated microscopically. The correlation of magnetic resonance imaging and histopathology was assessed using the kappa statistic. Overstaging with MRI was compared with Fischer's exact test. RESULTS: Histopathological examination of the tumors revealed adenocarcinoma. When the tumors were staged, there was one patient with a pT1 tumor, six patients with pT2 tumors, and 17 patients with pT3 tumors. Using MRI, four patients with pT2 were overstaged as T3, and one patient with pT3 was overstaged as T4. In the remaining cases (one pT1, two pT2, and 16 pT3), MRI correctly assessed the stage of transmural invasion. The accuracy of T staging and metastatic lymph node detection with MRI was calculated as 79.2% and 58.5%, respectively. CONCLUSION: Phased-array MRI is a valuable technique for the preoperative staging of rectal cancer, especially in the differentiation of T2 and T3 tumors.