Clinical relevance of 18F-FDG-PET/CT incidental findings

INTRODUCTION: The use of positron emission tomography with 2-deoxy-2-18F-fluoro-D-glucose integrated with CT (18F-FDG-PET/CT) in oncology is common. Unexpected incidental findings are occasionally recognised and can represent clinically relevant lesions or conditions. This study aims to assess the occurrence, clinical significance and economic impact of incidental 18F-FDG-PET/CT findings. METHODS: PET/CT of 670 cancer patients was evaluated in consensus by two experienced specialists within nuclear medicine and radiology. Foci with an abnormally increased 18F-FDG uptake and/or CT changes not related to the patients' disease were reported. Thirty-five foci in 29 patients were assessed and their cost and impact on patient management were analysed with up to 32 months of follow-up. A supplementary literature review was conducted using PubMed, Embase and Web of Science and the results were compared with ours. RESULTS: A total of 28 foci (80%) were clinically relevant and elicited management or follow-up including four malignancies and 18 premalignant and six benign lesions. Seven foci were without pathology. The estimated additional cost was 1,984 US$ per focus. In the literature review, 642 of 1,090 foci (59%) were relevant, distributed as 270 malignancies, 166 premalignant and 206 benign lesions, whereas 448 foci were without pathology. CONCLUSIONS: Incidental 18F-FDG-PET/CT findings should be investigated despite the occurrence of false-positive findings, additional time consumption and cost as they may represent obscure malignancies and premalignant or benign conditions needing treatment.