Predictors of Lateral Pelvic Lymph Node Metastasis in Advanced Low Rectal Cancer Treated With Neoadjuvant Chemotherapy

This retrospective study used magnetic resonance imaging to identify clinicopathological predictors of lateral pelvic lymph node metastasis in patients with advanced low rectal cancer treated with neoadjuvant chemotherapy; only few such studies have been reported.Sixty-one patients with advanced low rectal cancer who underwent total mesorectal excision and lateral pelvic lymph node dissection after neoadjuvant chemotherapy between April 2013 and December 2019 were included in this study. Univariate and multivariate analyses were used to analyze the relationship between lateral pelvic lymph node metastasis and clinicopathological factors, such as lateral pelvic lymph node size, measured before and after neoadjuvant chemotherapy using magnetic resonance imaging.The short-axis diameter of lateral pelvic lymph nodes before neoadjuvant chemotherapy (p=0.003, odds ratio: 2.898, 95% confidence interval=1.534-9.143) was the only identified independent preoperative predictor. Based on the receiver operating characteristic curve analysis, the cut-off value of the short-axis diameter of lateral pelvic lymph nodes before neoadjuvant chemotherapy was 6.8 mm. The area under the curve was 0.761 (95% confidence interval=0.723-0.932). The sensitivity, specificity, positive predictive value, negative predictive value, and accuracy were 77.8%, 72.1%, 53.8%, 88.6%, and 73.8%, respectively.The preoperative predictor of lateral pelvic lymph node metastasis in advanced low rectal cancer treated with neoadjuvant chemotherapy was the short-axis diameter of lateral pelvic lymph nodes before neoadjuvant chemotherapy. When lateral pelvic lymph nodes with short-axis diameters above 6.8 mm are present, lateral pelvic lymph node dissection may be necessary.