Abstract 721: Increased Fluorodeoxyglucose Uptake in the Abdominal Aortic Aneurysm (AAA) Wall Significantly Predicts the AAA Expansion Rate

Abstract

18-Fluorodeoxyglucose (FDG)-PET is capable to image active vascular inflammation. FDG uptake is seen frequently in the wall of abdominal aortic aneurysm (AAA) suggesting active areas of inflammation with unknown clinical significance. We hypothesized that focally increased FDG uptake in the AAA wall predicts accelerated AAA expansion. 20 patients who had a baseline oncologic PET/CT study and a follow-up PET/CT or CT study after 1 year were included. The AAA size in two dimensions and maximum standardized uptake value (maxSUV) in focally increased FDG uptake in the AAA wall on the baseline PET/CT and the AAA size on the follow-up study were recorded in similar position. A difference greater than 1 mm in size on repeated measurements in the largest dimension between the first and second study defined AAA progression. ROC curve analysis and t-test were used for statistical analysis. A p-value<0.05 defined statistical significance. 13/20 (65%) had an increase (G1), 7/20 (35%) had stable (G2) AAA size. Cardiovascular risk factors were similar between the groups (Male 53%, HTN 80%, Hypercholesterolemia 60%, DM 13%, Smoker 53%, CAD or CAD equivalent 100%, Statin use 53%). Mean AAA growth in G1 and G2 was 4.2 and 0.86 mm/year, respectively. Mean maxSUV in the AAA wall was significantly higher for G1 compared to G2 (2.88 vs. 2.03, p=0.0004). ROC analysis showed FDG uptake in the AAA wall to be an excellent test to predict AAA expansion as evidenced by an AUC=0.95. A maxSUV of 2.45 served as best cut-point to predict AAA expansion (sensitivity 92%, specificity 86%, p<0.001). The correlation between maxSUV and degree of AAA expansion was r=0.7 (p<0.001). After adjusting for all risk factors and statin use the maxSUV remained an independent predictor of AAA size progression (p=0.007). This is the first study to demonstrate that FDG uptake in the AAA wall significantly predicts the AAA size expansion. FDG-PET/CT may provide a mean to identify patients at high risk of AAA expansion and rupture.