Added Scans Caught Cancers That Mammograms Missed in Women With Dense Breasts

CATEGORY: WOMEN’S HEALTH

A screening mammogram comes back normal. When the breast tissue is dense, that clear result carries less reassurance than it sounds like it should. Among more than 9,000 UK women in exactly that position, a mammogram enhanced with contrast dye found about 19 additional cancers for every 1,000 women screened, a shortened MRI found about 17, and an automated ultrasound found about 4. Every one of those cancers had been invisible on an X-ray read as clear. The randomized trial was published in The Lancet.¹

White on White

Breast tissue counts as dense when it holds more glandular and fibrous tissue than fat. That takes in the two highest of the four standard density grades, which together cover close to half of women who have mammograms. The trouble is physics. On an X-ray, fat looks dark, but dense breast tissue looks white, and so does a tumor. Searching for one in the other is like looking for a snowball in a snowstorm. Dense tissue also carries a somewhat higher risk of breast cancer in the first place, so the women hardest to screen are among those with the most to gain from a better look.

Three Extra Scans, Ten Hospitals

The BRAID trial ran at ten UK hospitals and enrolled women aged 50 to 70 with dense breasts whose recent screening mammogram was normal. Each woman was sorted at random into one of three additional tests. The first was a shortened breast MRI, which uses magnets rather than X-rays. The second was contrast-enhanced mammography, a mammogram taken after an iodine dye is injected into an arm vein, so that the extra blood vessels a growing cancer recruits light up on the image. The third was an automated whole-breast ultrasound. This first planned report covers roughly 6,300 women who had completed their extra scan, about 2,000 in each group.

Nineteen, Seventeen, Four

Contrast-enhanced mammography detected 19.2 cancers per 1,000 women scanned and the shortened MRI 17.4. The automated ultrasound found 4.2. Most of what the top two methods picked up was invasive cancer, 15.7 and 15.0 per 1,000 respectively against 4.2 for ultrasound, and the tumors they caught were around half the size of those the ultrasound found. Small is what screening is after. In all, 85 cancers turned up in women whose mammograms had shown nothing.

Callbacks, Dye Reactions, and a Question Still Open

The sharper eyes came at a cost. Nearly one woman in ten scanned with MRI or contrast-enhanced mammography, 9.7% of each group, was called back for more testing, against 4% with ultrasound, and biopsies followed for 4.9% and 4.4% against 1.5%. Set those recall numbers beside the cancer numbers and the meaning of a callback is plain. Far more women were recalled than were found to have cancer, so a callback after a screening scan is a prompt for a closer look rather than a diagnosis. Among the roughly 2,000 women given the contrast dye, 24 had a reaction to it, one of them serious.

The researchers were direct about what the trial has not shown. Longer follow-up is needed to learn how these scans affect interval cancers, meaning the ones that surface between screening rounds, and overdiagnosis, the detection of cancers that would never have caused harm, and ultimately deaths from breast cancer. On the first of those, a Dutch randomized trial has already pointed one way. In women with extremely dense breasts, offering a supplemental MRI after a normal mammogram cut interval cancers in half: 2.5 per 1,000 women in the MRI-invited group against 5.0 per 1,000 with mammography alone.² Fewer cancers surfacing between screens is what would be expected if the extra scan is catching real disease earlier.

Key Takeaways

• In women with dense breasts and a normal mammogram, contrast-enhanced mammography found 19.2 cancers per 1,000 women and shortened MRI 17.4, roughly four times what automated ultrasound found at 4.2 per 1,000.
• The extra detection carried costs. Nearly one in ten women scanned with the top two methods was called back, and far more callbacks ended without a cancer diagnosis than with one.
• The trial measured detection, not survival. Whether finding these cancers earlier means fewer breast cancer deaths awaits longer follow-up.
• An earlier Dutch randomized trial found supplemental MRI halved the cancers that surface between screening rounds in women with extremely dense breasts.

References

1. Gilbert FJ, Payne NR, Allajbeu I, et al. Comparison of supplemental breast cancer imaging techniques—interim results from the BRAID randomised controlled trial. The Lancet. 2025;405(10493):1935–1944. link
2. Bakker MF, de Lange SV, Pijnappel RM, et al. Supplemental MRI Screening for Women with Extremely Dense Breast Tissue. New England Journal of Medicine. 2019;381(22):2091–2102. link