The re-evaluation of optimal lymph node yield in stage II right-sided colon cancer: is a minimum of 12 lymph nodes adequate?

Purpose Adequate lymphadenectomy is critical for accurate nodal staging and planning adjuvant therapy in colon cancer. However, the optimal lymph node (LN) yield for stage II right-sided colon cancer (RSCC) is still unclear. This population-based study aimed to determine the optimal LN yield associated with survival and LN positivity in patients with stage II RSCC. Methods All patients with stage II-III RSCC were identified from the Surveillance, Epidemiology, and End Results database over a 10-year interval (2006-2015). The optimal threshold for LN yield was explored using an outcome-oriented approach based on survival and LN positivity. Results The median number of LNs examined for all 17,385 patients with stage II RSCC was 17 (IQR 12-23). Nineteen LNs were determined as the optimal cut-off point to maximize survival benefit from lymphadenectomy. Increased LN yield was associated with a gradual increase in the risk of node positivity, with no change after 19 nodes. Compared with patients with 19 or more LNs examined, the group with fewer LNs had a significantly poor cancer-specific survival (< 12 nodes: hazard ratio (HR) 2.26, P < 0.001; 12-18 nodes: HR 1.58, P < 0.001) and overall survival (< 12 nodes: HR 1.80, P < 0.001; 12-18 nodes: HR 1.31, P < 0.001). Similar survival results were found in the validation cohort. Patients with older age, small tumor size, and appendix and transverse colon cancer were more likely to receive inadequate LN harvest. Conclusion A minimum of 19 LNs is needed to be examined for optimal survival and adequate node staging in lymph node-negative RSCC.