Classification of lymph node metastases from gastric cancer: comparison between N-site and N-number systems. Our experience and review of the literature.

The tumor, node, metastasis (TNM) system has become the principal method for assessing the extent of disease, determining prognosis in gastric cancer patients, and affecting the therapy strategies. The extent of lymph node metastasis is the most important prognostic factor. The aim of this study was to compare the N-classifications of the 4th and the 5th-6th TNM editions and to evaluate retrospectively the prognostic value of the 2002 TNM edition. We evaluated 344 patients who underwent curative total or subtotal gastrectomy. Nodal involvement was detected in 221 (64%) patients. Median follow-up period was 76 months. Thirty per cent of the old N1 patients were reclassified as pN2 (18.5%) and pN3 (11.3%). Eighty-eight per cent of the old N2 patients were reclassified as pN1 (75%) and pN3 (13.7%). In reclassifying the patients, statistically significant changes were reported between 1987 and 2002 TNM stage grouping, mainly in stage IIIB and IV. The 5-year survival rate per stage group did not statistically differ between the 4th and the 5th-6th editions, although a diminutive trend was registered in the IIIA stage. pTNM stage, nodal numerical stage, nodal topographical stage, and depth of tumor invasion resulted in significantly independent prognostic factors. Our data confirm the simplicity and easy application of the new stadiation and the better prognostic stratification of the N-stage. The pN3 group showed a worse prognosis independent of location. On the other hand, prognostic value of pN1 and pN2 stage is lower, probably depending on lymph node location. In multivariate analysis, the difference between old and new TNM staging is low. Hence, we suggest comparing lymph node location and number in larger series. In our series, in pT1 tumors, neither pN2 nor pN3 involvement was found. Hence, in our opinion, for correct N-staging, 10 lymph nodes in early gastric cancer and at least 16 in the other pT-stages seem sufficient for a real pN0 stadiation.