S477 Sensitivity and Specificity of FDG PET-CT Imaging for the Detection of Colonic Neoplasms

Introduction: Incidental colonic uptake observed on fluorodeoxyglucose positron emission tomography-computed tomography (FDG PET-CT) has been associated with the presence of colonic neoplasms. This study aims to evaluate the diagnostic performance of FDG PET-CT in detecting colonic neoplastic lesions. Methods: This IRB-approved retrospective cohort study included all adult patients at a single academic institution who underwent colonoscopy within 12 months of FDG PET-CT between January 1, 2010, and January 31, 2025. Clinical data were extracted from the electronic health record. A PET-CT scan was considered positive if there was any focal FDG uptake in the colon. Colonic neoplasia was defined as the presence of any of the following: hyperplastic polyp, tubular adenoma, sessile serrated adenoma, traditional serrated adenoma, tubulovillous adenoma, any adenoma with high-grade dysplasia, malignant lesions (colorectal origin or metastases), inflammatory polyp, or other polypoid dysplastic lesion. Descriptive statistics were used to classify PET-CT results as either true positive or false positive for positive scans, and true negative or false negative for negative scans, based on the presence or absence of neoplastic lesions on subsequent colonoscopy in the corresponding region or elsewhere in the colon. These classifications were then used to calculate the sensitivity and specificity of PET-CT for detecting 1) any colonic neoplasm and 2) advanced adenoma or colorectal cancer. Results: A query of the electronic health record identified 506 patients who underwent colonoscopy (with adequate bowel preparation) within 12 months of FDG PET-CT. Of these, 304 had negative PET-CT scans and 202 had positive PET-CT scans. Overall, PET-CT demonstrated a sensitivity of 25.4% and a specificity of 48.2% for the detection of any colonic neoplasm. For advanced adenomas and colorectal cancer, PET-CT showed a sensitivity of 51.2% and a specificity of 61.1%. Conclusion: While the sensitivity and specificity of FDG PET-CT for detecting advanced precancerous lesions and colorectal cancer remain inferior to those of established non-invasive screening modalities, this study underscores the importance of further evaluation with diagnostic colonoscopy when focal colonic FDG uptake is observed.