Association between Pathologic Grade and Multiphase Contrast-enhanced Computed Tomography Attenuation Level for Pancreatic Neuroendocrine Tumor

Abstract

Background/Aims: Pancreatic neuroendocrine tumors (PNETs) are rare diseases but gradually increasing in prevalence with different prognosis. Neuroendocrine tumors are classified into low-grade (G1), intermediate grade (G2), and high-grade (G3, neuroendocrine carcinoma) by WHO 2010 grading system. Prognostic validity of WHO grading system has been established by several studies. Multiphase contrast-enhanced computed tomography (CT) is known as the most useful imaging modality for the diagnosis of pancreatic tumors. We aimed to investigate whether CT enhancement pattern is associated with the pathologic tumor grades according to WHO classification and can predict those of pancreatic neuroendocrine tumor. Methods: Between January 2011 and December 2015, Ninety patients who underwent multi-phase contrast-enhanced CT and were diagnosed as pancreatic NETs histopathologically were retrospectively reviewed. The diagnosis of a PNETs were established by histopathological examination and immunohistochemistry on tissue samples, based on the 2010 WHO classification. Results: Ninety pancreatic NETs included sixty-two G1 (68.9%), twenty-one G2 (23.3%), seven G3 (7.8%). The enhancement values of the early arterial phase were significantly different among three groups (G1 vs. G2

p=0.043, G1 vs. G3

p=0.001, G2 vs. G3

p=0.027). In the late arterial phase, there was a difference between grade 1 and grade 3, grade 2 and 3, but no significant difference between grade 1 and grade 2 (G1 vs. G2

p=0.804, G1 vs. G3

p=0.016, G2 vs. G3

p=0. 0.022). The enhancement value of the portal phase did not differ significantly between the three groups. In G1 and G2, mean CT attenuation values highly increased in arterial phases and after which declined in portal phase. Enhancement values of G3 tumors showed no statistical difference between late arterial and portal phases. ROC analysis of the early arterial enhancement value for the differentiation of the grade 1 tumors was comparable to the tumor size. Conclusion: CT enhancement value of early arterial phase and degree of change among arterial phases can be help for the differentiation of pathologic grade of pancreatic neuroendocrine tumors