RSNA: Ultrasound+MRI screening for breast cancer benefits moderate- to high-risk women
The utilization of ultrasound, when combined with mammography, increases the detection rate of invasive cancers by approximately 34 percent and the utilization of MRI even further increased the detection rates of breast cancers to 67 percent, based on the findings of a study presented by Wendie A. Berg, MD, PhD, breast imaging specialist at American Radiology Services at Johns Hopkins in Lutherville, Md., during the Radiological Society of North America (RSNA) annual conference in Chicago earlier this month.

According to Berg, lead researcher of the study, the important goal is the detection of small (10 mm) node breast cancers, with invasive breast cancers being the most important to detect as these cancers can spread to the lymph nodes and throughout the body.

The study provided strong evidence of the benefit of annual screening with ultrasound and MRI for women with dense breast tissue who were at elevated risk for breast cancer, said Berg.

“With mammography, there is very good performance when the tissue is relatively fatty, and much easier than in a patient with dense breast tissue,” explained Berg.  “Unfortunately, there is no way knowing if the tissue is dense without doing a mammogram or perhaps an MRI.”

Berg noted that the U.S. Preventative Services Task Force two years ago recommended that anyone considered high risk for breast cancer (approximately 2 percent of this patient population) should have an annual MRI in addition to mammography.

“There are plenty of studies to support performing MRI in this situation,” said Berg.  “We know that mammography is very limited and women tend to be diagnosed with late-stage disease if we rely solely on mammography in this subgroup of women.”

In addition, Berg believes women in this subgroup should begin screening at the age of 30.

However, Berg noted that a much larger group of women fall into an intermediate risk category. Women can be categorized into this subgroup if they have a family history of breast cancer (providing an overall lifetime risk of 15-20 percent), a personal history of cancer, an atypical biopsy result or having dense breast tissue.

The study included 21 centers in the U.S., Canada and Argentina, recruiting 2,809 women of intermediate and high risk to participate--with the majority of participants falling into the intermediate category. Each woman underwent annual mammography and ultrasound screenings for three years. At the third year mark, a subgroup of women were offered MRI screenings at 14 of the centers.

Berg reported that a significant number of women refused the option for additional screenings with MRI (42 percent) citing claustrophobia, frail medical conditions and/or intolerance to MRI due to medical devices within the body and financial reasons. Many insurance companies refuse reimbursements for MRI screening for breast cancer.

The study found that the sensitivity with ultrasound and mammogram combined is 82 percent. Of the cancer found by ultrasound alone, 94 percent of cases were invasive, marking a 34 percent absolute increase in overall cancer detection, said Berg.

Despite the results, Berg noted the downside of ultrasound. “There was a 5 percent biopsy increase. Of those biopsies, 10 percent came back positive,” said Berg.

Those who had undergone MRI saw an even further increase in cancer detection, with a 67 percent absolute increase in invasive cancer detection. Moreover, those who had a mammogram and MRI do not need an ultrasound, said Berg.

The disadvantage to MRI, noted Berg, was that the study found 14 percent of women were recommended for follow up, a 10 percent overall increase to mammogram alone. Of this number, one in 13 of the participants required a biopsy.

The study recommends that women of average to intermediate risk should receive annual mammograms beginning at age 40, unless the woman has a personal history with cancer. For these cases, screening should be started immediately following that diagnosis.

For high-risk women, according to Berg and colleagues, MRI is highly sensitive and should be performed in addition to mammogram. Furthermore, ultrasound is a reasonable alternative for those women who cannot tolerate MRI.

“Women should ask their doctors what their breast density is and discuss risk factors with her doctor. If she chooses to have additional screening with MRI and ultrasound, it is important she recognizes the risk of a false-positive result.  Lastly, [the woman] should make sure that the facility where she receives the screening has the ability and expertise to perform a biopsy if needed,” concluded Berg.