Ki-67 Index of 5% is Better Than 2% in Stratifying G1 and G2 of the World Health Organization Grading System in Pancreatic Neuroendocrine Tumors

Abstract

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.