Survivals of patients with surgically treated and High-grade pancreatic neuroendocrine carcinomas: A comparative study between two American Joint Committee on Cancer 8th tumor-node-metastasis staging systems.

BACKGROUND AND
OBJECTIVE: We aimed to compare the two new defined tumor-node-metastasis (TNM) systems in the American Joint Committee on Cancer (AJCC) 8th staging manual for overall survival (OS) analysis of G3 pancreatic neuroendocrine carcinomas (p-NECs) that are currently proposed for pancreatic exocrine adenocarcinomas (p-EACs) and G1/G2 pancreatic neuroendocrine tumors (p-NETs), respectively.
METHODS: The data of patients who were surgically treated and histopathologically diagnosed with G3 p-NECs at West China Hospital of Sichuan University from January 2002 to June 2017 were retrospectively analyzed and compared using the two new AJCC staging systems.
RESULTS: Applying the p-EAC AJCC 8th TNM staging system to G3 p-NECs, the estimated 3-year OSs for each stage were 86.7%, 76.0%, 44.5% and 20.7%, respectively (P < 0.001). According to the G1/G2 p-NETs staging system, the estimated OSs at 3 years for each new AJCC stage were 100.0%, 83.6%, 47.1% and 20.7%, respectively (P < 0.001). The system for p-EACs significantly discriminated the survival difference of G3 p-NECs between Stage I and Stage II (P = 0.019), while the other one for G1/G2 p-NETs could not (P = 0.108). The consistent results of Akaike information criteria with Harrell's concordance index indicated that the AJCC 8th staging system for p-EACs was superior when applied to G3 p-NECs for its better prognostic stratification and more accurate prediction ability for OS.
CONCLUSIONS: Our analysis demonstrated that both TNM systems in the AJCC 8th staging manual were prognostic for patients with G3 p-NECs; however, the classification originally applied to p-EACs was superior and supported its use in clinical practice.