Optimal number of lymph nodes to be examined in stage II colon cancer

Abstract

Objective: to determine the minimum number of lymph nodes (LN) required for accurate prediction of overall survival in patients with stage II colon cancer and to assess the prognostic value of criteria used in the MOSAIC trial. Materials and methods. This retrospective study included patients with stage II colon cancer that underwent surgical treatment in the Department of Proctology and received adjuvant chemotherapy (if needed) in the Department of Clinical Pharmacology and Chemotherapy of N.N. Blokhin National Medical Research Center of Oncology between 2004 and 2013. Overall survival was considered as the main criterion of treatment efficacy. Results. A total of 445 patients met the inclusion criteria; of them, 60 (13.5 %) patients received adjuvant chemotherapy. The receiver operating characteristic (ROC) analysis was employed to evaluate the predictive value of the number of removed LN for disease progression and death in patients with stage II colon cancer. We found that specificity of >80 % was achieved by removing/examining at least 12 LN. The examination of 13 LN increases specificity by another 6 %. Further increase in the number of removed/examined LN (>13) did not significantly improve prognostic accuracy for death from the moment of disease progression. Only the removal of 13 or more LN ensured a significant impact on overall survival (hazard ratio (HR) 0.12; 95 % confidence interval (CI) 0.02—0.91; p = 0.04). At multivariate analysis, the following factors were found to affect overall survival: postoperative complications (HR 2.4; 95 % CI 1.4—4.3; p <0.01), pT4 stage (HR 1.2; 95 % CI 1.003—1.400; р = 0.04), and removal/examination of 13 or more LN(HR 0.1; 95 % CI 0.02—1.01;p = 0.05). However, after the inclusion of the variable reflecting the number of factors form the MOSAIC trail into the multivariate model, the last 2 covariates lost their statistical significance as independent prognostic factors. Conclusion. We recommend removing/examining at least 12 (preferable 13) LN in patients with stage II colon cancer in order to ensure proper staging. For patients with high risk of disease progression (those with <13 LN removed and/or presented a T4 depth of invasion in the intestinal wall), adjuvant chemotherapy should be considered. For routine clinical practice, we recommend assessing the risk of progression using the criteria from the MOSAIC trial for patients with stage II colon cancer.