Prevalence and malignancy risk of focal colorectal incidental uptake detected by 18F-FDG-PET or PET/CT: a meta-analysis

Background. The aim of the study was to meta-analyze published data about prevalence and malignancy risk of focal colorectal incidentalomas (FCIs) detected by Fluorine-18-Fluorodeoxyglucose positron emission tomography or positron emission tomography/computed tomography (F-18-FDG-PET or PET/CT). Methods. A comprehensive computer literature search of studies published through July 31st 2012 regarding FCIs detected by F-18-FDG-PET or PET/CT was performed. Pooled prevalence of patients with FCIs and risk of malignant or premalignant FCIs after colonoscopy or histopathology verification were calculated. Furthermore, separate calculations for geographic areas were performed. Finally, average standardized uptake values (SUV) in malignant, premalignant and benign FCIs were reported. Results. Thirty-two studies comprising 89,061 patients evaluated by F-18-FDG-PET or PET/CT were included. The pooled prevalence of FCIs detected by F-18-FDG-PET or PET/CT was 3.6% (95% confidence interval [95% CI]: 2.6-4.7%). Overall, 1,044 FCIs detected by F-18-FDG-PET or PET/CT underwent colonoscopy or histopathology evaluation. Pooled risk of malignant or premalignant lesions was 68% (95% CI: 60-75%). Risk of malignant and premalignant FCIs in Asia-Oceania was lower compared to that of Europe and America. A significant overlap in average SUV was found between malignant, premalignant and benign FCIs. Conclusions. FCIs are observed in a not negligible number of patients who undergo F-18-FDG-PET or PET/CT studies with a high risk of malignant or premalignant lesions. SUV is not reliable as a tool to differentiate between malignant, premalignant and benign FCIs. Further investigation is warranted whenever FCIs are detected by F-18-FDG-PET or PET/CT.