Evaluation of the prognostic relevance of the recommended minimum number of lymph nodes in colorectal cancer-a propensity score analysis.

PURPOSE Nodal status in colorectal cancer (CRC) is an important prognostic factor, and adequate lymph node (LN) staging is crucial. Whether the number of resected and analysed LN has a direct impact on overall survival (OS), cancer-specific survival (CSS) and disease-free survival (DFS) is much discussed. Guidelines request a minimum number of 12 LN to be analysed. Whether that threshold marks a prognostic relevant cut-off remains unknown. METHODS Patients operated for stage I-III CRC were identified from a prospectively maintained database. The impact of the number of analysed LN on OS, CSS and DFS was assessed using Cox regression and propensity score analysis. RESULTS Of the 687 patients, 81.8% had ≥ 12 LN resected and analysed. Median LN yield was 17.0 (IQR 13.0-23.0). Resection and analysis of ≥ 12 LN was associated with improved OS (HR = 0.73, 95% CI: 0.56-0.95, p = 0.033), CSS (HR 0.52, 95% CI: 0.31-0.85, p = 0.030) and DFS (HR = 0.73, 95% CI: 0.57-0.95, p = 0.030) in multivariate Cox analysis. After adjusting for biasing factors with propensity score matching, resection of ≥ 12 LN was significantly associated with improved OS (HR = 0.59; 95% CI: 0.43-0.81; p = 0.002), CSS (HR = 0.34; 95% CI: 0.20-0.60; p < 0.001) and DFS (HR = 0.55; 95% CI: 0.41-0.74; p < 0.001) compared to patients with < 12 LN. CONCLUSION Eliminating biasing factors by a propensity score matching analysis underlines the prognostic importance of the number of analysed LN. The set threshold marks the minimum number of required LN but nevertheless represents a cut-off regarding outcome in stage I-III CRC. This analysis therefore highlights the significance and importance of adherence to surgical oncological standards.