Is there a minimum number of lymph nodes that should be histologically assessed for a reliable nodal staging of T3N0M0 colorectal carcinomas?

BACKGROUND AND OBJECTIVES: Because of the existing controversy, we searched for a cutoff value for the number of lymph nodes (LNs) to be examined in order to establish a reliable node-negative stage in colorectal carcinomas (CRCs). METHODS: From the SEER database, 8,574 T3N0M0 first, single, histologically confirmed, surgically treated CRCs, with at least 1 LN examined histologically, were considered. As a first approach, the relationships between number of examined LNs and 5- and 10-year overall survival (OS) rates, computed by the Kaplan-Meier method, were assessed. Next, multivariate analysis was performed; a proportional hazards model was fitted to the data and used to obtain a smoothed plot of the martingale residuals vs. the number of negative LNs. RESULTS: Both OS rates displayed an improvement with an increase of number of LNs examined. The smoothed plot of the martingale residuals against the number of negative LNs was reasonably linear. CONCLUSIONS: Both approaches suggest that there is no cutoff value for the number of LNs to be examined for an adequate nodal staging; for a reliable pN0 staging, as many LNs should be assessed as possible. However, qualitative features of lymph nodes (e.g., those identified by sentinel lymphadenectomy) may alter this recommendation.