Abstract:
Objective In the recent edition of the TNM staging system, pN3b gastric cancer was subclassified for better prognostic accuracy.pN3b is defined as a large range of metastatic lymph nodes (mLNs). However, few studies have evaluated the prognosis of pN3b patients; furthermore, whether these patients were reasonably assigned to the same substage remains unknown.
Methods In total, 642 pN3b patients from a multi-institutional cohort in China were included. Disease-specific survival (DSS) was estimated using the Kaplan-Meier method, and independent prognostic factors were identified using Cox proportional hazards regression analysis. A restricted cubic spine model was used to assess the association between continuous variables and logarithm hazard ratios (HRs). The optimal mLN cut-off value for DSS was identified using the X-tile software.
Results The 5-year DSS rate of the total pN3b cohort was 15.4%. Smooth curves showed a non-linear association between mLNs and logarithm HRs. All pN3b gastric cancer patients were assigned into two subclassifications (pN3b1: 16-24 mLNs, pN3b2: ≥25 mLNs). A significant survival difference was observed between the two subclassifications (P=0.048). Additionally, the examination of more LNs could bring survival benefit only to pN3b1 patients but not to pN3b2 patients.
Conclusions We proposed a novel subclassification that assigned pN3b patients into two subclassifications with significant survival differences. Future studies should explore prognostic value based on this novel subclassification in the TNM staging system.