Preoperative Staging of Rectal Cancer Using Magnetic Resonance Imaging With External Phase-Arrayed Coils

HYPOTHESIS: Rectal cancer can be accurately staged preoperatively by magnetic resonance imaging (MRI) with external phase-arrayed coils. DESIGN: Comparison of MRIs with pathologic staging. SETTING: University hospital. PATIENTS: Twenty-eight consecutive patients with biopsy-proven rectal cancer who did not undergo irradiation. INTERVENTION: Patients underwent imaging using a 1.5-T MRI scanner with external phase-arrayed surface coils. Streaking of the perirectal fat and disruption of the bowel wall margin were interpreted as transmural invasion. Lymph nodes were defined as metastatic when they had a diameter of at least 0.5 cm. Tumors were staged according to the TNM staging system (American Joint Committee on Cancer guidelines) as confined to the bowel wall (T1-T2) and invading through the bowel wall (T3-T4). Patients underwent anterior resection (n = 15), abdominoperineal resection (n = 11), or local excision (n = 2). MAIN OUTCOME MEASURES: Calculation of sensitivity, specificity, and accuracy for invasion through the bowel wall and lymph node status. RESULTS: Sensitivity of MRI in detecting invasion through the bowel wall was 89% (16/18), specificity was 80% (8/10), and accuracy was 86% (24/28). Sensitivity for malignant lymphadenopathy was 67% (8/12), specificity was 71% (10/14), and accuracy 69% (18/26). CONCLUSION: Although more costly and not as accurate as endoscopic ultrasound, MRI with phase-arrayed coils had excellent sensitivity at detecting transmural penetration of rectal cancer.