Breast MRI Best Supplemental Screening for Dense Breasts
In women with dense breasts, breast MRI was better at detecting cancer than other supplemental screening methods, according to a study.
The research was published online on Jan. 31, 2023, by the journal Radiology. Read “Supplemental Breast Cancer Screening in Women with Dense Breasts and Negative Mammography: A Systematic Review and Meta-Analysis.”
What are dense breasts?
Your breasts are made up of fibrous tissue, glandular tissue (the tissue that produces milk), and fatty tissue. If you have dense breasts, it means you have more fibrous and glandular tissue and less fatty tissue than women who don’t have dense breasts. Having dense breasts is normal; it is not a medical condition itself, and it does not cause symptoms. You can’t tell whether or not you have dense tissue by feeling the breasts. Dense breast tissue can only be seen on a mammogram. Fatty tissue appears dark on a mammogram, and dense tissue appears white. About half the women who have mammograms have dense breasts and about 10% of women have extremely dense breasts.
Dense breasts are associated with a risk of breast cancer that is up to four times higher than the average. This higher risk is partially because it can be hard to see cancers in mammograms of dense breasts. Like dense breast tissue, cancerous tissue looks white on a mammogram.
Detecting cancer in dense breasts
Mammograms are the main tool doctors use to screen for breast cancer. When digital mammograms replaced film screen mammograms as the standard of care, the effectiveness of mammograms in detecting cancer improved by 14%.
But even digital mammograms have a hard time finding cancer in dense breasts. Statistics show that screening mammograms help find up to 98% of cancers in fatty breasts, but find only 30% to 48% of cancers in extremely dense breasts.
Doctors have suggested certain supplemental screening tests to help find cancer in dense breasts. The most common additional screening tests are:
As its name suggests, hand-held breast ultrasound uses a small, portable device to send high-frequency sound waves through the breast. The sound waves are converted to images on a viewing screen. Hand-held ultrasound screening finds between two and 2.7 more cancers that have not spread to the lymph nodes than mammography alone in women with dense breasts.
Still, specially trained technicians must perform hand-held breast ultrasound and the test has been shown to have high recall rates, as well as high false-positive biopsy rates.
Recall is when you’re called back for more tests if an area on the ultrasound looks suspicious. If the suspicious area turns out to be normal, it’s called a false positive. In some cases, doctors still may not be able to tell if an area is cancer or not until they do a biopsy. If the biopsy shows the area is normal, it’s called false-positive biopsy.
Because of the high recall and false-positive biopsy rates, many experts think this supplemental screening method isn’t cost effective.
Instead of a hand-held device, automated breast ultrasound uses a larger machine to send high frequency sound waves through the breast while you’re lying on your back on an exam table.
Automated whole-breast ultrasound screening finds 2.5 more cancers per 1,000 screenings in women with dense breasts than mammography alone. Like hand-held ultrasound, automated whole-breast ultrasound has high recall and false-positive biopsy rates. Also, automated whole-breast ultrasound can’t be used to evaluate suspicious findings or guide biopsies, so doctors have to order a hand-held ultrasound if automated whole-breast ultrasound finds a suspicious area.
Three-dimensional (3D) mammography (also called digital breast tomosynthesis, digital tomosynthesis, or just tomosynthesis) creates a 3D picture of the breast using X-rays. Several images from different angles around the breast are used to create the 3D picture.
A traditional mammogram creates a two-dimensional (2D) image of the breast from two X-ray images of each breast.
3D mammography was approved by the U.S. Food and Drug Administration (FDA) in 2011 and is a standard of care for breast cancer screening. Still, 3D mammography may not be available at all hospitals and mammogram facilities.
3D mammography finds between 2.2 and 2.5 more cancers in dense breasts than traditional 2D mammograms.
Breast MRI, or magnetic resonance imaging, uses magnets and radio waves to produce detailed cross-sectional images of the breast. In some cases, you may have to have a contrast solution or dye injected into your arm through an intravenous line.
Breast MRI finds 15.5 more cancers per 1,000 screenings in women with an average risk of breast cancer, especially in women with dense breasts.
Still, breast MRI has some drawbacks. It’s expensive, it’s not widely available, and it has been shown to have a high false-positive rate.
About the study
Although studies strongly suggest that additional breast cancer screening can benefit women who have dense breasts, few clinical guidelines directly recommend any of the supplemental screening methods.
In this study, the researchers looked at previously published research to compare the effectiveness of each supplemental screening option in women with dense breasts who’d had a normal mammogram.
This study is a meta-analysis, which combines and analyzes the results of a number of earlier studies. In this case, the researchers looked at 22 studies that included 261,233 women who had breast cancer screening, of which 132,166 were women with dense breasts who’d had a normal mammogram.
Among the women with dense breasts who’d had a normal mammogram:
71,921 were in a study on hand-held ultrasound
22,540 were in a study on automated whole-breast ultrasound
30,684 were in a study on 3D mammograms
7,021 were in a study on breast MRI
Overall, supplemental screening found 541 cancers among the women with dense breasts that were missed by mammography.
According to the researchers’ analysis:
breast MRI found 25.7 more cancers per 1,000 screenings than mammography
3D mammograms found 4.8 more cancers per 1,000 screenings than mammography
automated whole-breast ultrasound found 4.3 more cancers per 1,000 screenings than mammography
handheld ultrasound found 4.3 more cancers per 1,000 screenings than mammography
Breast MRI was better than the other supplemental screening methods at finding both invasive breast cancer and DCIS, which is non-invasive breast cancer.
“MRI is far superior in terms of cancer detection compared to hand-held ultrasound, automated ultrasound, and digital breast tomosynthesis,” Vivianne Freitas, MD, MSc, assistant professor at the University of Toronto, said in a statement. “Our results about the role of MRI in supplementary screening will allow stakeholders to guide healthcare policies in this setting and direct further research.
“Before we can advocate for wider application of breast MRI in these women, further evaluation of cost-effectiveness of breast MRI compared to other techniques, effect on mortality reduction, etc., will need to be studied,” Dr. Freitas added. “At the current time, availability and cost of the breast MRI remain the biggest barrier for widespread implementation.”
What this means for you
If you’re unsure whether you have dense breasts, it’s a good idea to look at your last mammogram report or talk to your doctor.
In the United States, 38 states and Washington, D.C., require breast imaging centers to give women some level of information about breast density after their mammogram. U.S. federal law requires that all women receive a letter notifying them about the results of their mammogram.
In most states, this form letter also tells you if you have dense breasts, and in some states, it lets you know your specific density category. The letter’s content varies widely by state and may not necessarily include specific details about your situation. Most of the letters advise you to discuss your results with your doctor. Your breast density is also included in the final mammography report to your healthcare provider, prepared by the radiologist who read the images.
If you live outside the United States, you may or may not be notified about your breast density, depending on your country’s regulations. DenseBreast-info.org is a good resource for finding out what the laws are where you live.
Right now, supplemental screening for dense breasts isn’t the standard of care, so not all health insurance companies offer coverage. It depends on the laws in your state. In some cases, supplemental screening may be covered if ordered by a healthcare provider. DenseBreast-info.org maintains a map of legislation by U.S. state and also has information for people in Europe. Ask your doctor for recommendations if you’re concerned about extra screening for dense breasts.
You and your doctor should discuss your individual situation, including the amount of dense breast tissue you have and whether you have other breast cancer risk factors. You also should discuss the cost of supplemental screening, what options are available in your area, and whether those tests are covered by your health insurance.
Learn more about cancer screening for women with dense breasts.
Editor’s Note: In March 2023, the FDA updated mammography regulations to make breast density reporting a national requirement. Each mammography facility must give women information about the density of their breasts, using specific language explaining how breast density can affect the accuracy of a mammogram and recommending that women with dense breasts talk to their doctors about breast density and how it affects their personal risk of breast cancer.
— Last updated on May 25, 2023 at 3:13 PM