The American Cancer Society has issued new guidelines that urge women at high risk of breast cancer to get annual MRIs, as well as mammograms.
The guidelines, the first to recommend magnetic resonance imaging for screening women who show no signs of cancer, are directed at women aged 30 and older.
They also target women who have a mutation in the BRCA1 or BRCA2 genes; those who were treated for Hodgkin's disease; those with a family history of the disease; women with two or more close relatives who had breast or ovarian cancer; or who have a close relative who developed breast cancer before age 50.
Typically, doctors screen women for breast cancer with mammograms, an X-ray technique that can reveal dense masses such as tumours.
MRIs make more detailed images with a magnet and radio waves, but without radiation.
Magnetic resonance imaging is also better at showing increased or abnormal blood flow in the breast -- a sign of early cancer -- and at detecting cancer in women with dense, non-fatty breasts.
But MRIs are not recommended for most women. One reason is the error rate, which can lead to unnecessary biopsies, and the long wait times.
"Certainly within Canada, MRI screening is available, and we need to think about access and how quickly women can get into an MRI screening program," Heather Logan, director of cancer control policy with the Canadian Cancer Society, told CTV.ca.
But Logan added that it will likely take time to ensure that Canada has the capacity to meet demand.
But the use of MRI as a screening tool should not be an arbitrary decision, she said.
Women must be clear on "who is being defined as high risk for breast cancer, and who isn't. And by being clear who is high risk, we are really making the most judicious decisions about the use of MRI as a screening tool," Logan said.
The guidelines were announced the same day a new medical study was released, suggesting all women newly diagnosed with breast cancer should get MRIs.
The New England Journal of Medicine reported the findings from a national study that suggests women who have cancer diagnosed in one breast should get an MRI in the other
The study found that scans revealed cancers in the opposite breast that were missed by ordinary mammograms in 3 per cent of these cancer survivors.
The study, led by Dr. Constance Lehman of the University of Washington Medical Center, looked at nearly 1,000 women recently diagnosed with cancer in one breast but who had no detected cancer in the second breast.
MRIs that scanned the second breast found possible tumours in 121 of the women. Biopsies confirmed that 30 of those women had cancer.
"It's a pretty striking effect," Dr. Carl Jaffe of the National Cancer Institute, which sponsored the study, told The Associated Press.
But the study does not suggest women should seek MRIs rather than mammograms, which are better at spotting calcium deposits, said Dr. Etta Pisano of the University of North Carolina, one of the study's authors.
"The take-home message of our paper is not, 'Don't get mammography.' It's 'Get MRI and mammography,'" she said.
With files from The Associated Press
