The study: Researchers looked at whether screening with molecular breast imaging (MBI) could detect more breast cancers than screening with mammography for women with dense breasts and an increased risk of breast cancer. In an MBI, a radioactive tracer is injected into a patient's body that is absorbed by breast tissue. A special camera is used to distinguish between healthy breast cells and cancerous breast cells. Although mammography is the standard screening option, it can be difficult to locate a tumor in women with dense breasts.

Researchers screened 940 women with both MBI and mammography. All women included in the study had dense breasts, determined by a previous mammogram, and they had an increased risk of breast cancer due to personal or family history, a genetic mutation related to breast cancer, a previous precancerous condition, or previous radiation therapy to the chest. Follow-up screening was performed for 375 women about 15 months or longer after the original screening to determine if they had been accurately diagnosed.

The results: MBI detected 3 times as many cancers in women who had dense breasts and increased breast cancer risk than mammography. Among the women in the study, 13 tumors in 12 women were found: eight with MBI only, one with mammography only, two with both screening methods, and two with neither screening method. About 8% of women who received MBI needed follow-up testing compared with approximately 9% of women who received mammography. Biopsies were performed on 36 of the tumors discovered by MBI and 17 of those discovered by mammography. About 28% of the tumors discovered by MBI were cancerous when biopsied compared with about 18% of tumors discovered by mammography.

Among the women who received follow-up screening, 75% who received MBI were accurately diagnosed with breast cancer compared with 25% of the women who received mammography. Approximately 93% of women who received MBI were accurately determined to not have cancer compared with 91% of women who received mammography.

What this means for patients

“These results suggest that MBI could become an important screening tool for women who have dense breasts and increased breast cancer risk,” said lead author Carrie B. Hruska, PhD, Research Fellow in the Department of Radiology at the Mayo Clinic in Rochester, MN. “More research is needed, but it is encouraging to find that MBI can detect cancers that are not easily visible on mammography.” MBI is only available at a limited number of cancer centers. For more information, talk with your doctor about your risk of breast cancer and the screening methods that are available in your area.