Mayo Clinic News

In the largest-ever study to compare molecular breast imaging (MBI) to mammography, researchers have shown that MBI can detect three times as many cancers in women who have dense breast patterns on their mammogram and are at increased risk of breast cancer. Mammography is the current standard of care for breast cancer screening. However, with mammography it is difficult to distinguish normal breast tissue from tumor tissue in women with dense breasts. As a consequence, women who have dense breasts as well as other breast cancer risk factors often need additional screening.

The study results are being presented this week at the American Society of Clinical Oncology’s 2008 Breast Cancer Symposium in Washington, D.C.

Note: See video and still images at the bottom of this post, along with an audio file.

MBI is a relatively new screening method that, while more expensive than mammography, is about one-fifth of the cost of breast MRI (magnetic resonance imaging). With MBI, patients are injected with a short-living radioactive agent that is absorbed by breast tissue. This agent is tracked with a specialized camera that can distinguish healthy tissue from breast cancer tumors, as cancer cells absorb more of the radioactive agent than healthy cells. MBI is currently available at a limited number of cancer centers, but its availability is growing.

“These results suggest that MBI could become an important screening tool for women who have dense breast tissue and increased breast cancer risk,” said Carrie B. Hruska, PhD, a research fellow in the Department of Radiology at Mayo Clinic in Rochester, Minn. “Larger trials are needed to further validate our research, but it is encouraging to find that MBI can detect cancers that are not easily visible on screening mammography. Our next step will be to compare MBI prospectively to other screening methods, such as MRI.”

Nine hundred and forty women were included in this study and were screened with both MBI and mammography. Participants had to meet two criteria. First, their breasts were determined to be dense by a previous mammogram. Second, 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 a history of radiation therapy to the chest.

A total of 13 tumors in 12 patients were detected: eight by MBI alone, one by mammography alone, two by both techniques, and two by neither. The recall rates (the number of women who needed follow-up testing) were 7.7 percent for MBI versus 9.4 percent for mammography. Of the 36 biopsies prompted by MBI, 27.8 percent were positive for cancer; of the 17 biopsies prompted by mammography, 17.6 percent were positive for cancer.

Researchers are continuing to follow all of the patients in the study, and so far 375 have been followed for 15 months or longer after the initial screening. Based on follow-up screening in these women, researchers determined the sensitivity (percent who were accurately diagnosed as positive for the disease) and specificity (percent of women who were accurately diagnosed as negative for the disease) of the two techniques. The sensitivity and specificity for MBI were 75 percent and 93.2 percent, respectively. By comparison, the sensitivity and specificity for mammography were 25 percent and 91.3 percent, respectively.

Below are images relating to the study. Click each to view full size.

Dr. Hruska provides an overview of the study in this video clip:

Here is an audio file of Dr. Hruska’s overview.

Update: Here is the Associated Press article about the study, along with the Reuters account.

Further Update: On Thursday, Sept. 4, ABC World News Tonight covered the story.