Accuracy of High-Resolution Magnetic Resonance Imaging in Preoperative Staging of Rectal Cancer

To achieve better prognosis and quality of life for patients with rectal cancer, extent of surgery and neoadjuvant chemoradiotherapy should accurately reflect disease extent. The aim of this study was to evaluate accuracy of high-resolution magnetic resonance imaging (HRMRI) for preoperative staging of rectal cancer. Between 2001 and 2003, 104 patients with primary rectal cancer were examined with HRMRI and underwent radical surgery. Transmural invasion depth and lymph node metastasis were assessed prospectively and classified according to the American Joint Committee on Cancer (AJCC) tumor-node-metastasis (TNM) system by both HRMRI and histopathology, and results were compared. Criteria for mesorectal and lateral pelvic lymph node involvement were short-axis diameters of a parts per thousand yen5 mm and a parts per thousand yen4 mm, respectively. There were 15 pT1, 25 pT2, 50 pT3, and 14 pT4 tumors. Overall accuracy rate for transmural invasion depth was 84%. The mesorectal fascia could be visualized in 98% of patients. Twenty-three patients had mesorectal fascia involvement and the overall accuracy rate was 96% (sensitivity, 96%; specificity, 96%). Fifty-three patients had mesorectal lymph node metastasis and the overall accuracy rate was 74% (sensitivity, 83%; specificity, 64%). Lateral pelvic lymph node metastasis was observed in 15 patients and the overall accuracy rate was 87% (sensitivity, 87%; specificity, 87%). HRMRI was moderately accurate for prediction of mesorectal lymph node metastasis and highly accurate regarding transmural invasion depth, and mesorectal fascia and lateral pelvic node involvement. Therefore, HRMRI appears useful for preoperative decision-making in rectal cancer treatment.