Tu1918 Correlation Between the 18F-FDG Uptake Assessed by PET/CT and Pathological Data in Well-Differentiated Digestive Neuroendocrine Tumors

The 18F-FDG uptake assessed by PET/CT is correlated to prognosis in most tumors. The aim of our study was to compare the 18F-FDG uptake with tumor proliferation (Ki67) and expression of molecules related to cell metabolism [hypoxia (VHL), glucose transport (GLUT1), regulation of cellular pH (CA9)] in well differentiated digestive neuroendocrine tumors (NET). Patients and Methods: This retrospective study included 22 patients. 18F-FDG uptake was assessed by the SUVmax value (Standardized Uptake Values). An immunohistochemical study was performed with Ki67, VHL, GLUT-1 and CA9 antibodies. A score (0-300) was calculated for each antibody. Results: NET were of pancreatic (15), midgut (3), esophageal (1), rectal (1), undetermined origin (2). 7, 9 and 6 tumors were of grade 1, 2 and 3 respectively; the average/median Ki67 was 15.86%/12% [1-60%]. The mean/median SUVmax was 6.26/5.09 [1.47 to 18.70]. Two tumor with SUVmax <2 were considered as negative at PET scan. Grade 1, 2 and 3 tumors exhibited a median SUVmax 4.45 [1.62 to 6.6]; 5.79 [1.46 to 18.7] and 6.7 [3.05 to 9.61] respectively. The SUVmax correlated with high tumor size (p=0.009), high Ki-67 (p=0.03) and low VHL expression (p=0.08). Conclusion: Our study highlights that well-differentiated digestive neuroendocrine tumors, even of grade 1, are frequently positive at PET scan. The accumulation of 18 F-FDG increases with tumor size and cell proliferation in these tumors and seems to be correlated with the expression of effectors of cellular metabolism.