Prognostic Factors and Long-Term Outcome of Pancreatic Neuroendocrine Neoplasms: Ki-67 Index Shows a Greater Impact on Survival than Disease Stage. The Large Experience of the Spanish National Tumor Registry (RGETNE)

Abstract

Introduction: Pancreatic neuroendocrine neoplasms (PNENs) are uncommon neoplasms with a wide spectrum of clinical behavior. The objective of this study was to assess in a large cohort of patients the relative impact of prognostic factors on survival. Methods: From June 2001 through October 2010, 1,271 patients were prospectively registered online (www.getne.org) at the Spanish National Cancer Registry for Gastroenteropancreatic Neuroendocrine Tumors (RGETNE) by participating centers. Clinical and histopathological features were assessed as potential prognostic factors by uni- and multivariate analyses. Results: Of 483 PNENs, 171 (35%) were functional (F) and 312 (65%) non-functional (NF). NF-PNENs were associated with a higher incidence of histological features denoting more aggressive disease, such as poor tumor differentiation, Ki-67 >20%, or vascular invasion (NF- vs. F-PNENs, respectively, p < 0.05). Nevertheless, functionality was not a significant predictor of survival (p = 0.19). Stage at diagnosis, Ki-67 index, tumor differentiation and surgical resection of the primary tumor were all significant prognostic factors in univariate analysis. However, Ki-67 (>20 vs. ≤2%) (hazard ratio (HR) 2.21, p = 0.01) and surgical resection (yes vs. no) (HR 0.92, p = 0.001) were the only independent predictors of survival in multivariate analysis. Among patients who underwent surgery, high Ki-67 index (HR 10.37, p = 0.02) and poor differentiation (HR 8.16, p = 0.03) were the only independent predictors of clinical outcome. Conclusion: Ki-67 index and tumor differentiation are key prognostic factors influencing survival of patients with PNENs and, in contrast to what it is observed for other solid malignancies, they seem to have a greater impact on survival than the extent of disease. This should be borne in mind by physicians in order to appropriately tailor therapeutic strategies and surveillance of these patients.