Objective: The World Health Organization (WHO) grading system for the stratification of G1 and G2 pancreatic neuroendocrine tumors (pNETs) using an optimal Ki-67 index cutoff is still controversial. The present study aimed at finding one optimal Ki-67 cutoff value that distinguishes G1 and G2 tumors by analyzing the prognosis of patients with pNET in our center.
Methods: Data from 84 patients with pNET undergoing surgical resection in The First Affiliated Hospital of Sun Yat-sen University between March 2003 and October 2015 were retrospectively analyzed.
Results: The 5-year overall survival rate was 74.2%. Univariate analysis revealed that functional secretion, WHO grade, and TNM stage were significantly associated with long-term survival (all P < 0.05). Multivariate analysis demonstrated that WHO grade (P = 0.023) and TNM stage (P = 0.040) were independent prognostic factors. The receiver operating characteristic curve showed that the Ki-67 index of 5% had the best predictive ability (76.7%) for 5-year survival with a hazard ratio of 44.7. The hazard ratio was only 8.14 when the Ki-67 index cutoff was 2%.
Conclusions: TNM stage and WHO grade were independent prognostic factors of pNETs. A Ki-67 index of 5% is better than 2% in stratifying G1 and G2 pNET tumors.