Reassessment of the Current American Joint Committee on Cancer Staging System for Pancreatic Neuroendocrine Tumors

BACKGROUND: Adopting a unified staging system for pancreatic neuroendocrine tumors (PNETs) has been challenging. Currently, the American Joint Committee on Cancer (AJCC) recommends use of the pancreatic adenocarcinoma staging system for PNETs. We sought to explore the prognostic usefulness of the pancreatic adenocarcinoma staging system for PNETs. STUDY DESIGN: The Surveillance, Epidemiology, and End Results program data were used to identify patients with PNETs who underwent curative-intent surgical resection from 1983 to 2008. The discriminatory ability of the AJCC system was examined and a new TNM system was devised using extent of disease variables. RESULTS: In 1,202 patients identified, lymph node metastasis was associated with worse 10-year overall survival after resection (51% vs 63%; p < 0.0001), as was the presence of distant metastatic disease (35% vs 62%; p < 0.0001). The current AJCC system (recorded by the Surveillance, Epidemiology, and End Results program in 412 patients since 2004) distinguished 5-year overall survival only between stages I and II (p = 0.01), but not between stages II and III (p = 0.97), or stages III and IV (p = 0.36). By modifying the T stage to be based on size alone (0.1 to 1.0 cm, 1.1 to 2.0 cm, 2.1 to 4.0 cm, and >4.0 cm) and revising the TNM subgroups, we propose a novel TNM system with improved discriminatory ability between disease stages (stages I vs II; p = 0.16; II vs III; p < 0.0001; and III vs IV; p = 0.008). CONCLUSIONS: In this study evaluating the current AJCC staging system for PNETs, there were no significant differences detected between stages II and III or stages III and IV. We propose a novel TNM system that might better discriminate between outcomes after surgical resection of PNETs. (J Am Coll Surg 2014; 218: 188-195. (C) 2014 by the American College of Surgeons)