Impact of lymph node retrieval on surgical outcomes in colorectal cancers.

Background: Adequacy of lymph node sampling is fundamental to the accuracy of nodal status (N-status) assessment in colorectal cancers (CRCs). This study aimed to determine the minimum sampling number to achieve reliable prognosis and to look for any association between the positive lymph node ratio (LNR) and overall survival (OS). Pathological reports of 533 stages I-III CRC patients who underwent curative resection during the period from January 1998 to December 2007 were retrospectively reviewed with regard to the number of lymph nodes obtained for pathological diagnosis (nLN) and number of positive nodes.

Results: The median nLN was 10 nodes and the mean number of positive nodes was 1.7 nodes. On the N-status attribution plot, the cut-off point where the converging curves turned parallel was at 12 nodes. This cut-off was supported by the significant difference in OS between cases with nLN ≥ 12 (5-year OS 73.0%) and those with nLN < 12 (5-year OS 62.7%), (P-value < 0.01). Multivariate analysis showed that both nLN-12 and LNR were independent factors predicting survival probability.

Conclusion: Our data emphasize the importance of lymph node harvesting during the surgical resection of CRCs. In addition, LNR is a strong independent factor associated with CRC survival.