Marchet A et al. (2007) The ratio between metastatic and examined lymph nodes (N ratio) is an independent prognostic factor in gastric cancer regardless of the type of lymphadenectomy: results from an Italian multicentric study in 1853 patients. Ann Surg 245: 543–552

There is evidence to indicate that, in patients with gastric cancer, the ratio of metastatic to examined lymph nodes (N ratio) might be a better prognostic tool than the TNM staging system. An Italian group has investigated this issue in a retrospective review of 1,853 patients who had undergone radical resection for histologically confirmed gastric carcinoma. They concluded that inclusion of the N ratio might improve the prognostic power of existing staging systems, even in cases in which only limited lymph node dissection is performed.

When patients were grouped by N stage, there were significant differences in 5-year overall survival between patients who had >15 lymph nodes examined and those who had ≤15 nodes examined. The data indicated that examination of 15 or fewer nodes resulted in understaging of patients. By contrast, 5-year survival did not vary with number of nodes examined when patients were grouped by N-ratio category (N ratio 0, 0%; N ratio 1, 1–9%; N ratio 2, 10–25%; N ratio 3, >25%; all categories determined by best-cutoff approach). The N-ratio categories identified groups of patients with significantly different survival rates; groups determined by N ratio were more homogenous than those determined by TNM classification. N ratio, but not N stage, independently predicted survival in multivariate analysis, regardless of the extent of lymph node dissection.