Women with an increased risk of breast cancer benefit from magnetic resonance imaging (MRI) screening, according to the American Cancer Society.
Based on new evidence, these women -- up to 1.4 million in the United States -- are now encouraged to get annual MRIs in addition to mammograms.
"ACS has recommended yearly breast cancer screening beginning at age 40 for some time now," said Dr. Robert Smith, director of cancer screening at the American Cancer Society. "But we have always known that there is a subgroup that is at greater risk, such as those who have a strong family history of the disease."
On the basis of new evidence, the guidelines now recommend annual MRIs for breast cancer screening for women with approximately 20 percent or greater lifetime risk of breast cancer.
This would include women with a strong family history of breast or ovarian cancer, as well as others who have specific mutations in BRCA1 or BRCA2, which are genes associated with breast cancer.
Women who have been treated with radiation to the chest for Hodgkin's disease should also have annual MRIs to check for breast cancer.
As the new guidelines were being announced, the New England Journal of Medicine also released the results of a national study today that suggest women who have cancer diagnosed in one breast should get an MRI of the other breast.
The study, led by Dr. Constance Lehman of the University of Washington Medical Center and the Seattle Cancer Alliance, looked at a total of 969 women with recent diagnoses of cancer in one breast and no abnormalities on clinical exam and mammography in the second breast.
They found that the MRI detected cancer in the opposite breast in 30 of 969 women (or 3.1 percent) who had recently been diagnosed with cancer in one breast only. The cancers in the opposite breast were missed by previous mammographies and clinical exams.
"When someone is first diagnosed with breast cancer, she has a 10 percent lifetime increased risk of getting another cancer in either of the breasts," said Dr. Carl Jaffe of the National Cancer Institute, which sponsored the study.
"Other cancers can be present at the time of diagnosis, and this study provides definitive evidence that an MRI can help detect them."
One of the advantages of detecting a second cancer early with an MRI is that it can then be treated simultaneously, thus avoiding another round of therapy at a later time when the tumor may also have progressed further.
Lehman said the research confirms that an MRI is a powerful tool in finding cancers that other screenings may miss.
"We have known from many smaller studies that breast MRI is a very powerful tool in detecting cancer," said Lehman. "This large multicenter study demonstrates that MRI will detect a significant number of cancers at an acceptable rate of false positive exams."
But experts are quick to warn that this does not mean that mammography be given up as a screening tool. MRI is only recommended for high-risk women, while mammography remains an important screening tool for all women.
"These new results do not mean that we throw out mammography altogether, but that we supplement it with MRI," said Dr. Mitchell Schnall, professor of radiology at the University of Pennsylvania and co-author of the study.