Diagnostic Performance of Multidetector Row Computed Tomography for Assessment of Lymph Node Metastasis in Patients with Distal Rectal Cancer

The accurate preoperative diagnosis of depth of tumor invasion and nodal status in distal rectal cancer is important because neoadjuvant chemotherapy or lateral pelvic lymph node dissection is indicated for patients with T3-T4 tumor or nodal involvement. This study aimed to determine the optimal cutoff value for predicting lymph node metastasis in patients with distal rectal cancer using multidetector row computed tomography (MDCT). The study investigated 77 patients who had undergone surgery for distal rectal cancer at a single institution between 2008 and 2011. Diagnostic performance for depth of tumor invasion and mesorectal and lateral pelvic lymph node metastases was evaluated. The optimal cutoff value was determined by receiver operating characteristic curve analysis. For predicting mesorectal and lateral pelvic lymph node metastasis, MDCT had a sensitivity of 0.36 and 0.89 and a specificity of 0.78 and 0.97, respectively. The optimal cutoff values of major and minor axes lengths for predicting mesorectal lymph node metastasis were 6.5 mm and 5.7 mm, respectively. The areas under the curve (AUCs) were 0.82 and 0.88, respectively. For predicting lateral lymph node metastasis, the optimal cutoff values were 9 mm for the major axis and 6 mm for the minor axis. Both AUCs were 1. Using MDCT, the optimal cutoff value of minor axis length for predicting mesorectal and lateral pelvic lymph node metastases in patients with distal rectal cancer was 6 mm. The accuracy of MDCT was satisfactory for predicting lateral pelvic lymph node metastasis.