Classification of lymph node metastases from carcinoma of the stomach: comparison of the old (1987) and new (1997) TNM systems.

The pN classification of gastric cancer is currently based on the distance of metastatic nodes from the primary tumor (TNM-1987). The UICC (Union Internationale Contre le Cancer) has recently proposed a new classification system based on the number of the involved nodes (TNM-1997). The present prospective study is aimed at verifying whether the two classifications (1) assign approximately a similar rank to individual patients and (2) give comparable prognostic information. The Cox regression model was used to evaluate the prognostic significance of either the distance or the number of positive nodes, controlling for sex, age, site, histology and depth of tumor invasion, in a group of 175 patients who underwent curative surgery for gastric cancer from March 1988 to October 1997. Among the patients classified as N1 and N2 according to TNM-1987, 81.8% (36/44) and 35.8% (19/53), respectively, were coded as N1 and N2 by the new classification. The survival probabilities of N1 and N2 categories were similar in both classifications. The N2 category of TNM-1987 comprised also 10 cases with >15 positive nodes (N3 category of TNM-1997), who presented a large excess mortality (RR = 35.14 with respect to N0). When the site and number of positive nodes are combined in a new variable, both appear to be important from a prognostic point of view. Both anatomic location and number of nodes with metastasis are important predictors of survival in gastric cancer patients. Caution should be used when replacing the old classification with the new one, as they group patients in a different way.