Lymph node evaluation and long-term survival in Stage II and Stage III colon cancer: a national study.

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.