18F-FDG PET and CT identifiers of high-risk lesions in the stomach and esophagus

e16036 Background: Assessing the significance of incidentally found increased 18F-FDG uptake in the stomach and esophagus on PET/CT has long been a challenge. Currently, there is no clear guideline to assist clinicians with distinguishing malignant from benign uptake. This study aims to compare various PET and CT characteristics used separately and collectively, to identify high-risk foci of uptake. Methods: 18F-FDG PET/CT images from August 2018 to October 2022 were reviewed and patients who completed a follow up EGD due to incidentally found increased gastroesophageal uptake were included in this study. To identify high-risk foci, the following PET and CT characteristics were used: 1) uptake intensity, using lesion SUVmax relative to mediastinal blood pool and liver SUVmean values (≤ blood pool = 0, > blood pool but < liver = 1, ≥ liver = 2); 2) uptake pattern (diffuse = 0, segmental = 1, focal = 2); 3) eccentricity (circumferential= 0, eccentric = 1); and CT correlation score (normal = 0, thickening = 1, mass = 2). Cut-off values were determined using receiver operating characteristic (ROC) curves. Benign and malignant uptake were compared to histological findings using Pearson’s chi-square test. Results: Incidental uptake in the stomach and/or esophagus were noted in 473/7805 (6.1%) patients of which 89 (18.8%) had a follow up EGD and were included in this study. Uptake intensity did not differentiate benign and malignant as SUVmax was greater than background tissues in all cases (Score =2). Uptake pattern, eccentricity, and CT-correlation of PET were significantly different between benign and malignant foci ( p < 0.001, p < 0.001, and p < 0.001, Chi-square). Using cut-off scores from ROC curves, the predictive value of different PET/CT characteristics in identifying high-risk foci was reviewed. Conclusions: PET eccentricity along with anatomic CT correlative findings, offer similar value in predicting high-risk uptake foci to uptake pattern, eccentricity, and CT correlation combined. These are both, however, superior to other PET/CT characteristics used alone or in combination. [Table: see text]