Breast MRI Better at Finding Disease in High-Risk Women, but Doesn’t Improve Outcome

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The American Cancer Society (ACS) recommends yearly breast cancer screening with both breast MRI (magnetic resonance imaging) and mammography for women with an abnormal breast cancer gene (BRCA1 or BRCA2), as well as women with a strong family history of breast cancer.

A study has found that breast MRI is better at finding breast cancer in high-risk women. Still, while MRI is more likely to find small breast cancers, it may not change overall outcomes for high-risk women who are diagnosed with breast cancer.

The research is published in the Nov. 19, 2011 issue of The Lancet.

Most inherited cases of breast cancer are associated with two abnormal genes: BRCA1 (BReast CAncer gene one) and BRCA2 (BReast CAncer gene two). Women with an abnormal BRCA1 or BRCA2 gene have up to an 85% risk of developing breast cancer by age 70. Their risk of ovarian cancer also is higher than average. Because of their substantially higher risk of breast cancer, more aggressive breast cancer screening makes sense for these women. More aggressive screening also may make sense for women who don't have an abnormal gene but do have a strong family history of breast cancer.

Researchers looked at the results from five studies examining the value of using breast MRI in the breast cancer screening plan of high-risk women. More than 3,810 high-risk women, many with an abnormal breast cancer gene, were in the studies.

Breast MRI was three times more likely than mammography to find breast cancer in high-risk women. Doctors say that breast MRI has three times the sensitivity of mammography for detecting breast cancer in high-risk women. This result strongly supports including both breast MRI and mammography in the screening plan of high-risk women.

But even though breast MRI was more sensitive than mammography, high-risk women who were screened with breast MRI and were diagnosed with breast cancer didn't have better overall survival than high-risk women who weren't screened with breast MRI and were diagnosed with breast cancer.

The results may seem to contradict each other. Breast MRI is better than mammography at finding cancer in high-risk women, yet that better detection doesn't improve overall survival when breast cancer is diagnosed.

Two things may be happening. First, early-stage breast cancer outcomes are very good with current treatments, so a small improvement in outcomes may be hard to detect in a study like this one. Second, women diagnosed with breast cancer may have several areas of cancer. Some of the areas may be so small that they're missed by mammography but found by breast MRI. Knowing about very small areas of cancer found by MRI but not mammography probably doesn't change a woman's treatment plan or response to treatment. So the overall outcome is the same when screening includes breast MRI.

Other research has found benefits to including MRI in the breast cancer screening plan of high-risk women. Until more is known, following the current ACS screening recommendations for high-risk women still makes sense. If you have an abnormal breast cancer gene, are at high risk for breast cancer because of a strong family history, or have a personal history of breast cancer, you and your doctor should develop a screening plan tailored to your specific situation. If the plan doesn't include breast MRI in addition to regular mammograms, you may want to talk to your doctor about the ACS recommendations and this study and ask if breast MRI screening makes sense for you.

You can learn more about mammograms, breast MRIs, and other breast cancer screening techniques in the Breastcancer.org Screening and Testing section.

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