Modified staging classification for pancreatic neuroendocrine tumors on the basis of the American Joint Committee on Cancer and European Neuroendocrine Tumor Society Systems

Purpose: The European Neuroendocrine Tumor Society (ENETS) and the American Joint Committee on Cancer (AJCC) staging classifications are two widely used systems in managing pancreatic neuroendocrine tumors. However, there is no universally accepted system. Methods: An analysis was performed to evaluate the application of the ENETS and AJCC staging classifications using the SEER registry (N = 2,529 patients) and a multicentric series (N = 1,143 patients). A modified system was proposed based on analysis of the two existing classifications. The modified system was then validated. Results: The proportion of patients with AJCC stage III disease was extremely low for both the SEER series (2.2%) and the multicentric series (2.1%). For the ENETS staging system, patients with stage I disease had a similar prognosis to patients with stage IIA disease, and patients with stage IIIB disease had a lower hazard ratio for death than did patients with stage IIIA disease. We modified the ENETS staging classification by maintaining the ENETS T, N, and M definitions and adopting the AJCC staging definitions. The proportion of patients with stage III disease using the modified ENETS (mENETS) system was higher than that of the AJCC system in both the SEER series (8.9% v 2.2%) and the multicentric series (11.6% v 2.1%). In addition, the hazard ratio of death for patients with stage III disease was higher than that for patients with stage IIB disease. Moreover, statistical significance and proportional distribution were observed in the mENETS staging classification. Conclusion: An mENETS staging classification is more suitable for pancreatic neuroendocrine tumors than either the AJCC or ENETS systems and can be adopted in clinical practice.