Prognostic stratification using a pathological nodal area involvement-based stage grouping in locoregional gastric neuroendocrine carcinoma.

BACKGROUND: Pathological nodal area involvement (pND), defined by the anatomical extent of nodal metastasis, has been associated with prognosis in gastric neuroendocrine carcinoma (NEC). However, whether pND can be incorporated into a clinical staging framework remains unknown. We developed a pND-based stage grouping combining pT category and pND status and evaluated its prognostic utility in patients with locoregional gastric NEC. METHODS: This multicenter study included 118 patients with locoregional gastric NEC who underwent curative gastrectomy with lymphadenectomy at 29 institutions. pND was classified as pND0 (no nodal metastasis), pND1 (metastasis confined to the D1 area), and pND2 (metastasis involving the D2 area). A pND-based stage grouping (Stages A-C) was constructed by combining pT category and pND status. RESULTS: Older age, female sex, and pND2 were independently associated with poorer overall survival (OS) and recurrence-free survival (RFS). For pND2, the hazard ratios were 2.50 (95% confidence interval (CI) 1.15-5.43) for OS and 2.76 (95% CI 1.32-5.77) for RFS. Stage C patients had markedly worse outcomes than those with Stage A or B disease. The pND-based grouping showed higher C-index values (OS, 0.62 vs. 0.58; RFS, 0.63 vs. 0.61) and lower AIC/BIC values than the UICC TNM classification, although the differences were not statistically significant. CONCLUSIONS: A pND-based stage grouping incorporating pT category and pND stratified prognosis in locoregional gastric NEC. Although not significantly superior to the UICC TNM classification, this framework may facilitate risk stratification in this rare disease.