Screening with MRI finds breast cancers at an earlier stage than mammograms in women with a family history of the disease, but this benefit may come with the risk of more overdiagnosis and false-positive results, especially in women with dense breasts, according to a Dutch study.
The research was published online on June 17, 2019, by The Lancet Oncology. Read the abstract of “MRI versus mammography for breast cancer screening in women with familial risk (FaMRIsc): a multicenter, randomised, controlled trial.”
Mammograms and MRI
A conventional mammogram creates a two-dimensional image of the breast from two X-ray images of each breast. Three-dimensional (3D) mammography (also called digital breast tomosynthesis, digital tomosynthesis, or just tomosynthesis), is a newer technology that creates a 3D picture of the breast, but that technology was not used in this study.
Magnetic resonance imaging — MRI — uses powerful magnets and radio waves to create detailed images of the organs and tissues in your body.
Overdiagnosis and false-positive results
Overdiagnosis means either:
- a breast cancer screening test finds a suspicious area that would have been eventually diagnosed as cancer by other means, without any effect on prognosis
- a breast cancer screening test finds a suspicious area that never would have affected a woman’s health if it hadn’t been found or treated
When a breast cancer screening test shows an abnormal area that looks like a cancer but turns out to be normal, it’s called a false positive. Ultimately the news is good: no breast cancer. But the suspicious area usually requires follow-up with more than one doctor, extra tests, and extra procedures, including a possible biopsy. There are psychological, physical, and economic costs that come with a false positive.
How the study was done
This study was done between Jan. 1, 2011, and Dec. 31, 2017, and included 1,355 Dutch women age 30 to 55 who had a lifetime risk of breast cancer of 20% or higher because of family history. None of the women had a BRCA1, BRCA2, or TP53 mutation, all of which are linked to a higher risk of breast cancer. Also, none of the women had been diagnosed with invasive breast cancer.
The women were randomly assigned to one of two screening programs:
- annual MRI and clinical breast exam, plus a mammogram every other year (675 women)
- annual mammogram and clinical breast exam (680 women)
Overall, MRI screening detected more breast cancers than mammography screening:
- MRI found 40 cancers
- mammography found 15 cancers
Invasive cancers detected were smaller in the MRI screening group:
- MRI found 24 invasive cancers with a median size of 9 millimeters (mm)
- mammography found 8 invasive cancers with a median size of 17 mm
The stages of the breast cancers found by MRI were earlier than the stages of the cancers found by mammography:
- 12 breast cancers in the MRI group and one cancer in the mammography group were stage T1a or stage T1b
- one cancer in the MRI group and two cancers in the mammography group were stage T2 or higher
In the TNM staging system, T describes the cancer tumor. T1, T2, T3, and T4 are based on the size of the tumor and the extent to which it has grown into nearby breast tissue. The higher the T number, the larger the tumor and/or the more it may have grown into breast tissue.
"We conclude that in real-life practice, MRI screening can result in an important and favourable shift in tumour stage at time of breast cancer detection compared with mammography screening, reducing the incidence of late-stage cancers and thus reducing the need for adjuvant chemotherapy and the risk of mortality," the researchers wrote.
Still, the researchers also said that the advantages of MRI screening might be at the cost of more false-positive results, especially in women with dense breasts. Other research has suggested that breast cancer screening with MRI leads to higher biopsy rates and these biopsies find fewer cancers than screening and biopsy with mammography.
What this means for you
If you have a higher-than-average risk of breast cancer because of family history, it’s a good idea to talk to your doctor about starting annual mammograms at a younger age and using other screening tools, such as MRI or ultrasound, to maximize the opportunity for early detection.
While breast cancer screening with MRI may lead to more false-positive results, a number of experts believe that overdiagnosis is better than underdiagnosis, especially in women who are age 50 and younger.
In an opinion piece that accompanied the research, Christiane Kuhl, M.D., of University Hospital Aachen in Germany, wrote, "In view of the devastating consequences of a late diagnosis of cancer, avoiding underdiagnosis should be deemed more important than avoiding overdiagnosis. We can alleviate much of the adverse consequences of overdiagnosis by providing patient information and appropriate selection of management."
In addition, earlier research found that while false-positive results do cause anxiety and stress for women, the anxiety is short-term and doesn’t affect a woman’s overall health and well-being.
For more information on the tests and tools used to screen for breast cancer, visit the Breastcancer.org Screening and Testing pages.
Written by: Jamie DePolo, senior editor
Reviewed by: Brian Wojciechowski, M.D., medical adviser