Prognostic significance of the number of lymph nodes examined in colon cancer surgery: clinical application beyond simple measurement.

OBJECTIVE

To identify an optimal cutoff value for the number of lymph node examined (NLNE) to distinguish the prognoses in patients following a curative resection for advanced colon cancer, to clarify the mechanism of the difference, and to suggest the integration of NLNE to colon cancer staging.

PATIENTS AND METHODS

A total of 859 patients who had undergone surgical treatment for localized colon cancer from 1980 to 2000 were reviewed. This was a cohort from a single institution with mean NLNE of 20.7 and more than 12 NLNE in 77% of the patients. The optimal breakpoint for NLNE was calculated by a receiver operating characteristic curve (ROC) analysis. The patients were stratified into groups based on various parameters and underwent univariate and multivariate analyses with respect to survival.

RESULTS

The ROC analysis identified NLNE as a significant prognostic factor with cutoff value of 18 for node-negative and 20 for node-positive patients. A multivariate analysis with these cutoff values identified NLNE as a significant prognostic factor independent of tumor depth and the number of lymph nodes involved. The 5-year cause-specific survival of stage IIB patients was 96.5% with 18 or more NLNE and 67.5% with NLNE less than 18 (P[r]=0.0067). Similarly, a cutoff value of 20 NLNE for node-positive patients separated the 5-year cause-specific survival of stage IIIB patients into 79.3% with 20 or more NLNE and 63.3% with less than 20 NLNE (P=0.0052).

CONCLUSIONS

The clinical significance of NLNE is not limited to being a benchmark for quality care, but has a definite benefit as a prognostic indicator across the stages. Patients could be stratified more efficiently by the integration of NLNE to TNM staging.