World Health Organization grading classification for pancreatic neuroendocrine neoplasms: a comprehensive analysis from a large Chinese institution

BackgroundPancreatic neuroendocrine neoplasms (p-NENs) are a group of highly heterogeneous tumors with distinct clinicopathological features and long-term prognosis. In 2017, in order to better stratify patients into prognostic groups and predicting their outcomes, World Health Organization (WHO) officially updated its grading system for p-NENs which distinguished these neoplasms among Grading 1 (G1) pancreatic neuroendocrine tumors (p-NETs), G2 p-NETs, G3 p-NETs and G3 pancreatic neuroendocrine carcinomas (p-NECs). However, this new grading classification for p-NENs has not yet been rigorously validated.MethodsData of patients who were surgically treated and histopathologically diagnosed as p-NENs at West China Hospital of Sichuan University from January 2002 to December 2018 were retrospectively collected and analyzed according the novel WHO 2017 grading classification.ResultsWe eventually enrolled 480 eligible patients with p-NENs in our present study, in which 150 patients with WHO 2017 G1 p-NETs, 158 with G2 p-NETs, 64 with G3 p-NETs and 108 with G3 p-NECs were identified. The estimated 5-year overall survival for patients with G1 p-NETs, G2 p-NETs, G3 p-NETs and G3 p-NECs was 75.8, 58.4, 35.1 and 11.1%, with a median survival time of 85.3mons, 67.4mons, 51.3mons and 26.8mons, respectively. Patients with G2 p-NETs present notably worse survival than those with G1 p-NETs (P=0.03). Survival of G3 p-NETs were significantly worse than that of G1 p-NETs or G2 p-NETs (P<0.001, P=0.023, respectively), as well as that when comparing G3 p-NECs with G1 p-NETs or G2 p-NETs (P<0.001, P<0.001, respectively). Patients with G3 p-NECs showed statistically shorter survival than those with G3 p-NETs (P<0.001). Both WHO 2017 and 2010 grading criteria could be independent predictor for the OS of p-NENs (P=0.016, P=0.022; respectively). The 95% confidence intervals of WHO 2017 grading classification (0.983-9.454) was slightly smaller than that of WHO 2010 criteria (0.201-13.374), indicating a relatively more accurate predicting ability for the prognosis of p-NENs.ConclusionThe WHO 2017 grading classification for p-NENs could successfully allocate patients into four groups with distinct clinical features and significant survival differences, which might be superior to the WHO 2010 criteria for its better prognostic stratification and more accurate predicting ability.