Lymph node staging in gastric cancer: new criteria, old problems.

Purpose: Our study aims to test the prognostic accuracy of the N parameter of the 7th TNM in a Western series of D1-gastrectomies for gastric cancer (GC).

Methods: Retrospectively considering a series of 224 non-metastatic GC patients who underwent surgery with curative intent and limited lymphadenectomy, we analyzed 5-year overall survival (OS) related to pN status according to both TNM editions (pN6 and pN7) and to lymph node ratio (LNR; LNR0, 0%, LNR1, 1-19%; LNR2, > 20%). We stratified pN6- and pN7-related OS by LNR.

Results: Both pN6 and pN7 were shown to significantly stratify different subsets of GC patients, but there was no significant difference between pN71 and pN72, nor between pN62 and pN63. A multivariate model specific for pN7 eliminated the N2 group, while the pN6 model maintained all 3 N groups with highly discriminating hazard ratios. LNR was able to further stratify one category of pN6 (N2) and two categories of pN7 (N1 and N2).

Conclusions: The 7th TNM edition for GC does not seem to be superior to the 6th edition in evaluating the prognostic relevance of lymph-nodal status: in particular, it does not allow an accurate stratification of OS in patients with less than 6 positive lymph nodes.