Breast density is gaining increasing attention, with South Carolina becoming the 27th US state to pass density notification laws last month. However, there is still an impasse in the medical community regarding clinical recommendations for women with dense breasts—how can that information be translated into saving lives? MRI screening is expensive and not available to all women, while ultrasound is susceptible to false positives. Molecular breast imaging (MBI) is a new adjunctive screening modality that can help with this. This new technology involves injection of a radiotracer (99mTc-sestamibi) to allow the energy-demanding cancer cells to be imaged via dual-head gamma cameras.
Shermis and his colleagues used information from a breast screening program in Ohio to select 1,696 women who had dense breasts (as measured by Volpara) but who would not qualify for supplemental MRI under the current ACS guidelines. MBI found an additional 13 cancers that were not detected by mammography and could have been missed altogether until symptoms developed. Furthermore, this screening modality is a potential improvement on what is currently available clinically. The set-up of an MBI machine is similar in cost and space requirements to that of a mammography unit, making it more affordable than MRI. In addition, MBI has improved specificity compared to ultrasound—MBI produces a two-fold improvement in terms of incremental cancer detection and a 2-4 fold improvement in terms of the positive predictive value for biopsies.