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

Abstract 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 values of 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 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 long-axis diameter and 5 mm for short-axis diameter of LPLN provides sufficient diagnostic accuracy for LPLNM.