Minimal apparent diffusion coefficient in predicting the Ki-67 proliferation index of pancreatic neuroendocrine tumors

Abstract

Purpose: To investigate the diagnostic performance of the minimal apparent diffusion coefficient (ADC_min) to distinguish between pancreatic neuroendocrine tumors (Pan-NETs) with low and high Ki-67 proliferation index values and to evaluate the relationship between ADC_min and the Ki-67 proliferation index.

Methods: Pre-operative magnetic resonance imaging data and postoperative Ki-67 proliferation index data of 42 patients with primary neuroendocrine tumor of the pancreas from November 2014 to March 2021 were included in this retrospective study. According to the Ki-67 proliferation index value, Pan-NETs were divided into a high-expression group (Ki-67 ≥ 10%, n = 17) and low-expression group (Ki-67 < 10%, n = 25), and mean ADC (ADC_mean) and ADC_min values were compared between groups using receiver operating characteristic (ROC) curves to evaluate the performance of ADC_mean and ADC_min in judging the expression level of Ki-67 proliferation index. The relationship between ADC_min and the Ki-67 proliferation index was also evaluated.

Results: The ADC_min was significantly higher in the low-expression group (Z = - 3.537, p < 0.01). The area under the ROC curve (AUC) for ADC_min was 0.825, which was higher than that for ADC_mean (0.781). Using 1.32 × 10^-3 mm²/s as the optimal discriminating threshold, the sensitivity, specificity, accuracy, and positive and negative predictive values of the two groups were 80%, 88.2%, 83.3%, 90%, and 75%, respectively. The ADC_min of Pan-NETs showed a significant negative correlation with the Ki-67 proliferation index (r_s = - 0.634, p < 0.001).

Conclusion: The ADC_min is a potential imaging biomarker, which may be helpful for non-invasive preoperative prediction of the Ki-67 proliferation index of Pan-NETs and the subsequent planning of appropriate treatment.

Keywords: Diffusion-weighted imaging (DWI); Ki-67 proliferation index; Minimal apparent diffusion coefficient (ADCmin); Pancreatic neuroendocrine tumor (Pan-NET).