Prevalence of Focal Incidental Breast Uptake on FDG-PET/CT and Risk of Malignancy: a Systematic Review and Meta-analysis

Background: FDG-PET/CT is increasingly used for oncologic and inflammatory diseases. Focal incidental FDG uptake occurs rarely in breast tissue but has often significant consequences. This study aimed to systematically review literature regarding focal incidental breast uptake (FIBU) on FDG-PET/CT in order to yield an update on the prevalence and risk of malignancy for FIBU.

Methods: A systematic search for relevant articles published between 2012 and 2018 was performed through MEDLINE, Embase, and Cochrane databases. Studies addressing the detection of FIBU in patients without a previous history of breast malignancy were included. The QUADAS-2 was used for quality assessment, and eligible data were pooled using a fixed-effects model. I was calculated for the heterogeneity between studies.

Results: Eight studies containing 180,002 scans were included in the systematic review. The median prevalence of FIBU for both genders was 0.52% (range 0.18-22.5%). Prevalence for women was mentioned separately in five studies and varied from 0.51 to 23.5%. One study reporting a high prevalence was based on patients being staged for known malignancy, and the word "breast" was used in the search, which may have caused selection bias. Data from four studies were eligible for meta-analysis. A high degree of heterogeneity was observed for prevalence data (I of 97.5%), while moderate heterogeneity was observed for data on malignancy risk assessment (I of 62.8%). The pooled prevalence of FIBU in women was 0.61% (range 0.56-0.66%), and the pooled prevalence of malignancy of FIBUs was 38.7% (range 34.4-43.0%). The most commonly detected malignancy was invasive ductal carcinoma.

Conclusion: FIBU occurs rarely on FDG-PET/CT for female patients but yields a high risk of malignancy according to the results of published papers. Therefore, it should be considered relevant to further elucidate patients with incidentally detected FDG uptake in breast in clinical practice.