Novel staging for gastric neuroendocrine neoplasms by incorporating the WHO grading into the TNM staging system

BACKGROUND: The 8th tumor‐node‐metastasis (TNM) classification of the American Joint Committee on Cancer (AJCC) can be used to estimate the prognosis of gastric neuroendocrine tumor (gNET) and gastric neuroendocrine carcinoma (gNEC) patients but not gastric neuroendocrine neoplasms (gNENs). METHODS: First, in the SEER (training) dataset, a TNMG system was built by combining the WHO G grade (G1‐4; NEC grouped into G4) with the 8th AJCC T (T1‐4), N (N0‐1), and M (M0‐1) stage, which was then validated in a Chinese (validation) cohort. RESULTS: In all, 2245 gNENs cases from the training dataset and 280 cases from the validation dataset were eligible. The T stage, M stage, and G grade were independent prognostic factors for OS in both datasets (all p < 0.05). The TNMG staging system demonstrated better C‐index for predicting OS than the 8th AJCC TNM staging system in both the training (0.87, 95%CI: 0.86–0.88 vs. 0.79, 95%CI: 0.77–0.81) and validation (0.77, 95%CI: 0.73–0.80 vs. 0.75, 95%CI: 0.71–0.79) datasets. The AUC of the 3‐year OS for the TNMG staging system was 0.936 and 0.817 in the SEER and validation dataset, respectively; higher than those of the 8th AJCC system (vs. 0.843 and 0.779, respectively). DCA revealed that compared with the 8th AJCC TNM staging system, the TNMG staging system demonstrated superior net prognostic benefit in both the training and validation datasets. CONCLUSIONS: The proposed TNMG staging system could more accurately predict the 3‐ and 5‐year OS rate of gNENs patients than the 8th AJCC TNM staging system.