MRI Provides Extra Screening for Breast Cancer in High-Risk Women

Women who have been diagnosed with breast cancer should have a magnetic resonance imaging (MRI) scan of the other breast in addition to mammography, says the American Cancer Society (ACS).

This test may help physicians find a small number of cancer cases missed by mammography, according to the New England Journal of Medicine.

The study found that MRI scans picked up 3 percent of cancers missed by mammography alone in women who had already been diagnosed with cancer in one breast.

"The results of this study will lead to changes in practice," says Dr. Etta Pisano, a study author and director of the Biomedical Research Imaging Center at the University of North Carolina at Chapel Hill School of Medicine.

"While this study does not suggest that MRI supplants mammography,” says Dr. Pisano, “I think what will end up happening is that all women with breast cancer will end up getting MRI" if they have had a normal mammography.

Test May Mistakenly Find Cancer in Some

The ACS has issued new guidelines recommending an annual MRI screen in addition to an annual mammography for women at high risk of breast cancer.

But, because the false-positive rate of MRIs was relatively high - about 11 percent in the new study - the authors do not recommend MRI as a screening tool for the general population.

For the new study, Dr. Pisano performed MRI scans on 969 women who had recently been diagnosed with breast cancer in one breast. Mammography did not detect abnormalities in the other breast of the women.

One hundred and twenty-one women had positive MRI findings, meaning they had suspected cancer in the other breast. Biopsies were done to confirm the cancer diagnosis.

Of those women, 30 (24.8 percent) were found to have cancer in the second breast - cancers that had not been detected with mammography.

But, the test was not perfect. It had a false-positive rate of 10.9 percent.

"The costs of false-positives have to be weighed against the cost of missing a cancer," explains Dr. Pisano, adding that for women who have already been diagnosed with breast cancer, the additional knowledge gained from the MRI outweighs the false-positive risk.

"For these women, because they're at such high risk, everything is worrisome,” says Dr. Pisano. “You really want to know that you're going to give them cancer therapy once, rather than twice.”

In an accompanying editorial in the journal, Robert A. Smith, director of cancer screening for the ACS, says the false-positive risk "is likely to be acceptable to women with unilateral breast cancer, since they will place a high priority on a thorough evaluation for the presence of other primary lesions."

Women with High Risk Benefit Most

Debbie Saslow, director of breast and gynecological cancers for the ACS, notes that because of the high false-positive rate, she is "doubtful there will come a time when we recommend both mammography and MRI regardless of risk."

For the average-risk woman, she explains, mammography is the screening tool of choice. And, Dr. Pisano points out that mammography can pick up very early cancers that an MRI scan may miss.

However, the ACS recommends an MRI in addition to mammography for high-risk women, such as those with a known genetic mutation that increases the risk of breast cancer.

In the new guidelines, the cancer society recommends an annual MRI screen in addition to an annual mammography for women who:

• have a BRCA 1 or 2 mutation, or are untested for these mutations but have a first-degree relative with a BRCA 1 or 2 mutation

• have a lifetime breast cancer risk higher than 20 percent (ask your doctor to assess your risk using standard risk assessment tools)

• have a known genetic mutation in the TP53 or PTEN genes or have a first-degree relative with either mutation

• received radiation treatment to the chest between the ages of 10 and 30

Saslow says these high-risk women represent only about 2 percent of the entire US population, so, for most women, these new guidelines do not apply.

An annual mammogram is all they need to effectively screen for breast cancer.

"So many women are so fearful of breast cancer, but most women aren't at high risk,” she says. “Since most women aren't in this category, they need to remember that mammography is a really good test. All women need to get a mammogram every year, starting at age 40."

Always consult your physician for more information.