What Is the Minimum Number of Examined Lymph Nodes After Neoadjuvant Therapy in Rectal Cancer?

Background To date, no guidelines have standardized the number of examined lymph nodes (eLNs) after neoadjuvant treatment. This study investigated the minimum number of eLNs required for patients with rectal cancer (RC) who received neoadjuvant treatment. Material and Methods This study was based on data from the Surveillance, Epidemiology, and End Results (SEER)-Medicare-linked database. We included 2173 patients with RC who received neoadjuvant therapy. Restricted cubic spline was used to analyze the association between eLNs and lymph node metastasis (LNM). Results The number of eLNs was an independent predictive factor for the presence of LNM (odds ratio 1.033; 95% confidence interval 1.020–1.046; P < 0.001). When the number of eLN ≤ 16, 10 and 11 eLNs had the highest rates of positive LNM. Analysis of the restricted cubic spline method found that when number of eLNs was < 10, the LNM rate increased rapidly, but this increase was not so obviously when there were > 10 eLNs. Conclusions Among RC patients who receive neoadjuvant therapy, the minimum number of eLNs may be 10 to ensure pathological quality.