Background ¹⁸F-FDG uptake in positron emission mammography (PEM): Correlation with mammographic density and background parenchymal enhancement in breast MRI

We aimed to determine whether background ¹⁸F-FDG uptake in positron emission mammography (PEM) was related to mammographic density or background parenchymal enhancement in breast MRI. Methods: We studied a total of 52 patients (mean age, 50.9 years, 26 premenopausal, 26 postmenopausal) with newly diagnosed breast cancer who underwent ¹⁸F-FDG PEM (positron emission mammography), conventional mammography and breast MRI. The background mean ¹⁸F-FDG uptake value on PEM was obtained by drawing a user-defined region of interest (ROI) in a normal area of the contralateral breast. We reviewed the mammography retrospectively for overall breast density of contralateral breast according to the four-point scale (grade 1-4) of the Breast Imaging Reporting and Data System (BI-RADS) classification. The background parenchymal enhancement of breast MRI was classified as minimal, mild, moderate, or marked. All imaging findings were interpreted by two readers in consensus without knowledge of image findings of other modalities. Results: Multiple linear regression analysis revealed a significant correlation between background ¹⁸F-FDG uptake on PEM and mammographic density after adjustment for age and menopausal status (P < 0.01), but not between background ¹⁸F-FDG uptake on PEM and background parenchymal enhancement on MRI. Conclusion: Background ¹⁸F-FDG uptake on PEM significantly increases as mammographic density increases. Background parenchymal enhancement in breast MRI was not an independent predictor of the background ¹⁸F-FDG uptake on PEM unlike mammographic density.