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 Roughly half of U.S. women in their 40s and 50s have dense breast
tissue, which increases their risk of breast cancer and makes it
harder to detect tumors with mammography. Several states require
healthcare providers to send notification letters to women whose
mammograms show dense breast tissue. Some states also require that
these higher-risk women be advised to get screened with ultrasound
or MRI.
"Dense breasts may mask small cancers on mammography," said Dr.
Christoph Lee, senior author of the study and a researcher at the
University of Washington and the Hutchinson Institute for Cancer
Outcomes Research in Seattle.
"Ultrasound is not influenced by breast density and may detect
additional cancers," Lee said by email.
To see whether dense breast notification laws changed how often
physicians ordered screening ultrasounds for women, researchers
examined data from 12,787 wellness visits from 2007 to 2015 by women
40 to 74 years old.
Overall, about 29% of the women had breast exams during their
checkups and 22% had a screening mammogram ordered, but just 3.3%
had screening ultrasounds ordered.
Screening ultrasound rates remained persistently low throughout the
study period, and didn't change after states passed dense breast
notification laws, which were on the books in 36 states as of
January 2019.
"Physicians may not recommend supplemental ultrasound for the
majority of women with dense breasts as the current evidence
suggests that risks outweigh benefits of screening ultrasound," Lee
said.
With ultrasound screening, more women with tumors may detect the
cancer sooner, when it's easier to treat, and early detection is the
motivation behind many state laws recommending dense breast
notification. But there is also a risk of so-called over-diagnosis,
which can cause women to undergo needless testing or treatments for
relatively harmless tumors.
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It's possible some doctors and patients discuss screening
ultrasounds and decide the risks aren't worth it, Lee said. It's
also possible that physicians don't order ultrasounds because there
isn't a nearby radiology facility that can do these tests or because
insurance may not cover it.
One limitation of the study is that researchers lacked data on how
many women got ultrasound screening, since the focus was on whether
physicians ordered the test, not whether women followed through.
A previous study of dense breast notification laws found that more
women did get screening ultrasounds when the laws required patients
to be told about the benefits of additional tests like ultrasounds
or MRIs.
In the current study, however, notification on its own didn't appear
to boost ultrasound screening rates.
It's possible this study found no change in ultrasound screening
after dense-breast-notification laws passed because some physicians
recommended MRIs instead, said Dr. Richard Bleicher, leader of the
breast cancer program at Fox Chase Cancer Center in Philadelphia.
"Breast MRIs are recommended and used frequently in women who have a
genetic predisposition for breast cancer; these women are those who
have a family history and get screened at a young age for a gene
mutation, or develop cancer at a young age and then get gene
tested," Bleicher, who wasn't involved in the study, said by email.
"Since MRIs are the predominant modality used (in addition) to
mammography in these younger women, these are the same women who
typically have the densest breasts, and screening ultrasound is
unlikely to replace breast MRI," Bleicher said.
SOURCE: https://bit.ly/2KpkX5X Journal of the American College of
Radiology, online July 18, 2019.
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