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: Nxn_1~6 and Nxn_≥7. N0, N1, N2, and N3 (the previous classifications) were replaced by N0, N1n_1~6, N2n_1~6, and N1n_≥7 + N2n_≥7 + N3n_1~6 + 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.