A new pN staging system based on both the number and anatomic location of metastatic lymph nodes in gastric cancer.

Background: Our aim was to establish a new pN staging system for gastric cancer based on the number and location of metastatic lymph nodes (MLNs) and to compare it with other systems.

Methods: We retrospectively analyzed the prognostic data of 521 gastric cancer patients who underwent curative resection. Survival analyses were used to establish a pN staging system that considers both the number and location of MLNs and to compare discriminatory ability and monotonicity of gradients (linear trend χ (2) score), homogeneity ability (likelihood ratio test), and prognostic stratification ability (Akaike information criterion) between Japanese Gastric Cancer Association (JGCA) and Union for International Cancer Control (UICC) systems.

Results: Cut-point survival analysis divided pN(+) patients into two groups: Nxn1~6 and Nxn≥7. N0, N1, N2, and N3 (the previous classifications) were replaced by N0, N1n1~6, N2n1~6, and N1n≥7 + N2n≥7 + N3n1~6 + N3n≥7, respectively. Compared with two widely used staging systems, the new system had the highest likelihood ratio test [106.06 (new) vs 95.09 (JGCA) vs 94.33 (UICC)] and linear trend χ (2) scores [102.30 (new) vs 89.12 (JGCA) vs 86.97(UICC)] and the lowest Akaike information criterion (AIC) score [2,283.88 (new) vs 2,285.31 (JGCA) vs 2,299.88 (UICC)].

Conclusion: A new pN staging system based on the number and location of MLNs is an efficient prognostic indicator of the survival of patients with gastric cancer following radical surgery.