Relationship Between 18F-FDG Uptake and Breast Density in Women with Normal Breast Tissue

Breast density affects the mammographic detectability of breast cancer. The study aimed to evaluate the impact of breast density on the 18 F-FDG uptake of normal breast tissue. Methods: The study population consisted of 45 women (median age, 54 y; age range, 42-77 y). All underwent whole-body 18 F-FDG PET for various indications other than breast cancer, and all underwent mammography within a mean of 6.6 ± 4.9 mo of PET. On the basis of mammographic findings, breasts were categorized as extremely dense, heterogeneously dense, primarily fatty, or entirely fatty. Regions of interest were drawn on every PET image in which breast tissue was visualized. Average and peak standardized uptake values (SUVs) were calculated for the left and right breasts. Results: Mammography showed that 20 of the 45 women had heterogeneously dense breasts, 1 had extremely dense breasts, 20 had primarily fatty breasts, and 4 had entirely fatty breasts. In dense breasts, the average SUV was 0.39 ± 0.05 (right breast) and 0.36 ± 0.07 (left breast) and the peak SUV was 0.93 ± 0.16 and 0.89 ± 0.18, respectively. The average and peak SUVs were significantly lower for primarily fatty breasts than for dense breasts (P < 0.01). Peak and average SUVs of entirely fatty breasts also differed significantly from peak and average SUVs of dense and primarily fatty breasts (P < 0.01). The impact of hormonal status on SUV was significant but less than the impact of breast density. No significant relationship between average SUV or peak SUV and age or serum glucose level was observed. Conclusion: Breast density and hormonal status affect the uptake of 18 F-FDG. Dense breasts exhibit, on average, significantly higher 18 F-FDG uptake than do nondense breasts. However, the highest peak SUV observed in dense breasts was 1.39, which is well below the SUV of 2.5 commonly used as a cutoff between benign and malignant tissue. Therefore, breast density is unlikely to affect the ability of 18 F-FDG PET to discriminate between benign and malignant breast lesions.