After breast cancer has been diagnosed, some doctors order a breast MRI (magnetic resonance imaging) to help them decide if mastectomy or lumpectomy should be recommended. The MRI is done to provide more information about the breast cancer, but there isn't good evidence that routinely using MRI in this way improves the doctor's recommendations, the care a woman receives, or the outcome of the treatment.
A study found that an MRI after breast cancer diagnosis and before surgery didn't really help doctors make better decisions about whether mastectomy or lumpectomy was the best option for a woman. In this study, doing an MRI for more information led to a longer time between diagnosis and the start of treatment. The research was presented at the 2008 American Society of Clinical Oncology (ASCO) Breast Cancer Symposium.
The researchers analyzed the treatment records of 577 women between 2004 and 2006; 130 women had a breast MRI done before surgery. The results:
- MRI before surgery became more common over time. In 2004, 13% of the women had MRI, compared to 41.5% in 2005, and 45.4% in 2006.
- Getting an MRI before breast cancer surgery delayed surgery. Women who had an MRI had about 57 days (almost 2 months) between diagnosis and surgery. Women who didn't have MRI had 38 days (slightly more than a month) between diagnosis and surgery.
- Women who had an MRI before surgery were almost twice as likely as women who didn't get an MRI to have mastectomy instead of lumpectomy.
- Having a mastectomy because MRI was done before surgery didn't improve treatment results or the overall outcome compared to lumpectomy.
During lumpectomy, a pathologist looks at the edges (also known as margins) of the tumor that's removed to make sure they're "clear" (don't have cancer cells). If the tumor margins have cancer cells, more tissue may need to be removed or a mastectomy may need to be done.
If MRI before surgery were helping doctors make better choices about who should get a mastectomy vs. lumpectomy, then the researchers should have found that women who had MRI and lumpectomy were more likely to have clear margins. This wasn't the case. About 22% of the women who had MRI and lumpectomy had cancer cells in the tumor margins, compared to 14% of the women who had lumpectomy and didn't have MRI. Some of the women with cancer cells in the tumor margins had to have mastectomy to make sure all the cancer was removed. About 10% of the women who had MRI before surgery ended up having mastectomy instead of lumpectomy, compared to about 6% of the women who didn't have MRI.
These research results don't mean that having an MRI before surgery is a bad idea. The results suggest that ROUTINELY doing an MRI before surgery may not make sense; routinely doing MRI before surgery may lead to more mastectomy recommendations than lumpectomy recommendations with no improvement in care or outcomes.
If you've been diagnosed with breast cancer and your doctor recommends an MRI to help make choices about surgery, ask your doctor why MRI is being recommended and how the results will help your care.
You can learn much more about tests to evaluate breast cancer, including MRI, in the Breastcancer.org Screening and Testing section.