LET’S BEGIN WITH THE RECENT PROVOCATIVE HEADLINE: Half of the women who have annual breast cancer screening with 3D mammograms with be told there is a concerning finding when there is no cancer present.
We’ll come back to that awful statistic, but we need to keep such findings in context: Randomized clinical trials show that screening mammograms save lives.
Today, I look forward to exploring breast cancer screening, including the pros and cons of the various imaging approaches.
Mammograms remain central to screening for breast cancer. Systematic reviews of randomized clinical studies for women ages 40 to 69 years show a long-term drop by up to one-fifth in the risk of dying from breast cancer.
Unfortunately, these are primarily historical; most screening mammograms studies began before 1990. Since then, there have been changes in imaging, and there have also been tremendous treatment advances.
Full-field digital mammography
Today, many patients have full-field digital mammograms. These images are similar to traditional film-screen mammograms, except now the image is captured by an electronic detector stored on a computer.
In the United States today, virtually all of the mammography units accredited by the Food and Drug Administration are full-field digital units. Are these newer digital mammograms better than the old film ones?
The most extensive study, the Digital Mammographic Imaging Screening Trial (DMIST), discovered that while the overall diagnostic accuracy of the film and digital mammograms appear similar, digital mammography is more accurate for women less than 50 years of age, for premenopausal and perimenopausal women, and women with dense breasts.
This digital approach produces three-dimensional (3D) images using a moving X-ray source with a digital detector. Multiple studies suggest that tomosynthesis mammograms increase cancer detection rates modestly compared with historical 2D digital mammograms.
A 2018 analysis of a collection of studies showed a gain of 1.6 cancers (per one thousand screening studies) detected with the addition of tomosynthesis, compared with traditional mammograms alone. The tomosynthesis rates also appeared lower.
Alas, no studies have examined whether tomosynthesis cuts breast cancer mortality chances.
Mammograms — Still the gold standard
Mammograms continue to be the primary imaging modality for screening women at average risk of getting breast cancer.
Ultrasound sometimes supplements mammogram screening for those with dense breasts, even though we don’t have high-level evidence to show improved outcomes.
Magnetic resonance imaging (MRI), in combination with mammograms, is being increasingly used for those at high risk of getting breast cancer. However, we have some data that incorporating MRI for those with extremely dense breasts (and normal results on mammograms) results in fewer interval (between studies) cancers than mammograms alone.
Mammograms — New findings
A University of California, Davis-led study, published 25 March 2022 in the Journal of the American Medical Association Network Open, reports these findings:
Half of women will experience a false-positive mammogram after ten years of annual breast cancer screening with 3D mammograms. The risk appears lower for women who have mammograms every other year.
The 3D mammogram approach modestly dropped the odds of having a false-positive result compared with standard digital 2D mammograms.
These groups had a lower false-positive risk:
- Women with non-dense breasts
- Older women
- Those who screened every other year
Writing in sciencedaily.com, the first author Dr. Michael Bissell writes that the “screening technology did not have the largest impact on reducing false positives.”
Dr. Bissell adds that the findings from our study highlight the importance of patient-provider discussions around personalized health. It is essential to consider a patient’s preferences and risk factors when deciding on screening interval and modality.
The researchers analyzed data collected by the Breast Cancer Surveillance Consortium on 3 million screening mammograms for over 900,000 women aged 40–79 years.
I am surprised that the innovative 3D mammogram approach for breast cancer screening did not lower the chances of having a false positive after ten years of screening. Still, mammograms save lives.