Breast cancer screening with 3D mammograms reduces the rate of interval cancers — cancers detected between routine screening — compared to 2D digital mammograms, according to a Swedish study.
The research was published online on April 6, 2021, by the journal Radiology. Read the abstract of “Interval Breast Cancer Rates and Tumor Characteristics in the Prospective Population-based Malmö Breast Tomosynthesis Screening Trial.”
What is 3D mammography?
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.
To start offering 3D mammograms, facilities must buy new mammography machines or update their existing machines to make them 3D capable. So not all facilities have been able to make the switch to 3D mammography because of large up-front costs for equipment. In other cases, facilities had rental agreements for 2D mammography equipment and had to wait until those leases ended to upgrade.
According to the FDA, more than 75% of U.S. screening facilities now offer 3D mammograms on at least one of their mammography units, but fewer than half of all accredited units are actually 3D-capable.
Also, not all insurance plans cover 3D mammograms. So some women must either pay out-of-pocket for a 3D mammogram or have a 2D mammogram.
A number of studies have found that 3D mammograms find more cancers than traditional 2D mammograms and that they also reduce the number of false positives.
A false positive is when a mammogram shows an abnormal area that looks like a cancer but turns out to be normal. 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.
About interval breast cancers
Interval breast cancers are defined by the National Cancer Institute as a cancer that is found between a screening mammogram with normal results and the next screening mammogram. Interval breast cancers tend to be larger and grow and spread more quickly than breast cancers found by a routine mammogram.
“Interval cancers have, in general, a more aggressive biological profile than screen-detected cancers,” explained study lead author Kristin Johnson, M.D., radiology resident at Skåne University Hospital in Malmö, and Ph.D. student at Lund University, Sweden, in a statement. “This means that the prognosis is less favorable for interval cancers compared to screen-detected cancers.”
Many screening programs require the rate of interval breast cancer detection to be reported because this rate is used to measure effectiveness. A reduced rate of interval breast cancers when screening with 3D mammograms may indicate that 3D mammograms are better than 2D mammograms at detecting rapidly growing cancers.
About the study
For this study, the researchers compared interval cancer rates in the Malmö Breast Tomosynthesis Screening Trial with interval cancer rates in a control group of women of the same ages who had digital 2D mammography at the same screening center. The women were screened between 2010 and 2015.
In Sweden, women who are age 40 to 54 have breast cancer screening every 1.5 years. Women who are age 55 to 74 have breast cancer screening every 2 years.
The 14,848 women in the Malmö Breast Tomosynthesis Screening Trial group had a 3D mammogram and a digital 2D mammogram at each screening appointment.
The 26,738 women in the control group had a digital 2D mammogram at each screening appointment.
The average age of the women in both groups was 56.
- 21 interval cancers were diagnosed in the women in the Malmö Breast Tomosynthesis Screening Trial group
- 76 interval cancers were diagnosed in the women in the control group
The interval cancer rates were:
- 1.6 per 1,000 women for the Malmö Breast Tomosynthesis Screening Trial group
- 2.8 per 1,000 women for the control group
The researchers calculated that the risk of interval cancer in the Malmö Breast Tomosynthesis Screening Trial group was 40% lower than the risk of interval cancer in the control group.
This is the first study to show a reduction in interval breast cancer rates with 3D screening mammograms compared to digital 2D screening mammograms.
Johnson cautioned that interval cancer rates, while important, are not the only way to measure the effectiveness of screening.
“Other factors, such as cancer types detected and cost-benefit, have to be taken into account,” she said.
What this means for you
If you aren’t sure your screening facility offers 3D mammograms, call and check before you make your appointment. If the facility doesn’t offer 3D mammograms, ask your doctor to recommend a facility that does.
If you aren’t sure if your insurance plan covers 3D mammograms, call and ask. Both Medicare and Medicaid now cover 3D mammograms.
In some states, such as Washington, there are laws that require facilities not to charge more for 3D mammograms. So even if your insurance doesn’t cover it, you can still get a 3D mammogram for the cost of a 2D mammogram, which in almost all states is free. In other states, such as New Jersey and Pennsylvania, there are laws that require insurers to cover 3D mammograms at no cost to women.
If you’re unsure about how much, if anything, you will have to pay for a 3D mammogram, call the facility and ask.
To learn more about 3D mammography, including how it’s done and how it’s different from 2D mammography, visit the Breastcancer.org Digital Tomosynthesis page.
Written by: Jamie DePolo, senior editor
Reviewed by: Brian Wojciechowski, M.D., medical adviser
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