Background: The most important prognostic factor in colonic cancer is the presence or absence of regional lymph nodes metastases. The aim of this study was to evaluate the relationship between 5-year mortality in the New Zealand population, and the number of nodes examined in Stage II and III colon cancers.
Methods: New Zealand Cancer Registry data were retrieved for patients with colonic cancer from January 1995 to July 2003. Patients with incomplete entries, Stage I tumors, and distant metastases were excluded from analysis. Univariate and Cox regression models were used with 5-year mortality as the primary endpoint.
Results: The study identified 4309 patients. Younger age, female gender, Pacific Island descent, and right-sided tumors were associated with significantly higher lymph node retrieval. Cox regression analysis showed that the number of nodes examined was a significant predictor of 5-year mortality when age, sex, ethnicity, and site were controlled for. Five-year survival consistently improved between nodal strata until the 16-node mark, above which survival advantage was minimal. For Stage III cancers, a higher lymph node ratio was associated with a significant increase in mortality.
Conclusions: Increased rates of nodal examination are associated with a significantly lower 5-year mortality for Stage II and III colonic cancer, but this survival advantage appears to be minimal after the 16-node mark. The lymph node ratio has been validated as a powerful predictor of survival in Stage III cancer. Our results support the current practice of harvesting and examining as many nodes as possible during attempted curative resection.