OBJECTIVE(S): Increasing the number of lymph nodes analyzed has been reported to correlate with improved survival in stage II colon cancer. We hypothesized that achieving a goal of analyzing a minimum of 15 nodes would improve the survival of patients with colon cancer undergoing potentially curative resections.
METHODS: The Surveillance, Epidemiology, and End Results database was queried for all patients undergoing colonic resection with histologically confirmed non-metastatic colon cancer between years 1988 and 2000. Patients were excluded if an unknown number of nodes was sampled. The number of nodes sampled was categorized into 1-7, 8-14, and >15 nodes sampled. Survival curves constructed using the Kaplan-Meier method were compared using log rank testing. A Cox proportional hazard model was created to adjust for age, race, gender, tumor grade, tumor size, and TNM stage.
RESULTS: 82,896 eligible patients were identified in the database. The median number of lymph nodes sampled for all patients was 9. For all stages, increasing nodal sampling was associated with improved survival (table). Multivariate regression demonstrated that patients who had least 15 nodes sampled as compared to 1-7 nodes experienced a 29% reduction in mortality independent of other patient and tumor characteristics.

AJCC Stage		Stage I		Stage II		Stage III
	n	22,143		34,741		26,012
# of Nodes Sampled		Median Survival (Months)	5 Year Survival	Median Survival (Months)	5 Year Survival	Median Survival (Months)	5 Year Survival
0	12,735	132**	74%	45**	45%	NA	NA
1-7	32,782	138	84%	77	66%	46	49%
8-14	32,147	131	83%	99**	70%	52**	51%
≥15	24,823	149*	87%	131**	78%	67**	57%
Median # of nodes		5		10		11
% cases ≥ 15 nodes		15%		29%		32%
* p value =0.001; ** p value <0.0001; reference group = 1-7 nodes

CONCLUSIONS: Adequate lymphadenectomy, as measured by meeting a guideline of at least 15 lymph nodes analyzed, correlates with improved survival, independent of stage, patient demographics, and tumor characteristics. Currently, the majority of patients do not meet this guideline. Future trials of adjuvant therapy should include extent of lymphadenectomy as a stratification factor and when reporting results.