Predictive Value of Preoperative Computed Tomography for Lateral Pelvic Lymph Node Metastasis in Rectal Cancer

Background Pretreatment diagnosis of lateral pelvic lymph node (LPLN) metastasis is critical in deciding the therapeutic strategy for locally advanced rectal cancer. We aimed to investigate computed tomography (CT) cut-off values and diagnostic and prognostic implications of lateral pelvic lymph node metastasis (LPLNM) in rectal cancer. Methods Patients with rectal cancer ( n = 126) who underwent primary tumor resection between April 2010 and July 2020 were included. CT findings and diagnostic accuracies were analyzed. Results In this study, the cut-off values of 7 mm for long-axis diameter and 5 mm for short-axis diameter were selected. At cut-offs of 7 mm for long-axis diameter, the sensitivity, specificity, positive predictive value, negative predictive value, and accuracy were 88.9%, 93.8%, 34.8%, 99.6%, and 93.7%, respectively. At cut-offs of 5 mm for short-axis diameter, the values of sensitivity, specificity, positive predictive value, negative predictive value, and accuracy were 88.9%, 90.9%, 26.7%, 99.5%, and 90.9%, respectively. CT findings of ≥ 7 mm for long-axis diameter (odds ratio, 68.0) and ≥ 5 mm for short-axis diameter (odds ratio, 38.4) were strong predictors of LPLNM. In the subgroup analysis of patients with enlarged LPLN (≥ 7 mm), higher recurrence-free survival and lower local recurrence rates were found in patients who had LPLN dissection (5-year recurrence-free survival: 100% vs. 58.3%, p = 0.17 with LPLN dissection; and 5-year local recurrence: 0% vs. 31.4%, p = 0.27, without LPLN dissection). Conclusion Pretreatment CT at cut-off values of 7 mm for the long-axis diameter and 5 mm for the short-axis diameter of LPLN provides sufficient diagnostic accuracy for LPLNM.