Although current mammogram guidelines say once every two years for women ages 50 to 74, some with dense breasts should get screened every year, while others may only need a mammo every three years, according to researchers.
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Many women may only need a mammogram once every three years, according to a new study, instead of the current government recommendation of every two years. The findings apply to a large percentage of women ages 50 to 74 who have lower breast density and average breast cancer risk. On the other hand, the study found, those with high breast density may be better off with more screenings—one every year.

The findings, published Monday in the Annals of Internal Medicine and sponsored by the National Cancer Institute, are simply a suggestion, says the author of an editorial published along with the study. They’re not meant to replace existing guidelines put out earlier this year by the U.S. Preventive Services Task Force (USPSTF), according to Christine Berg, MD, a radiation oncologist with Johns Hopkins Medicine in Bethesda, Maryland.

The current recommendations do advocate that women and their doctors take into account their individual preferences and risk factors when considering how often they should get mammograms, the study authors point out. But, there isn’t a lot of data to help people decide what, exactly, that means.

One known risk factor for breast cancer is having dense breasts, especially after menopause. So to see if women with dense breasts and women with fatty (also known as lower density) breasts might need different advice, the researchers, led by Amy Trentham-Dietz, PhD, of the University of Wisconsin–Madison in Wisconsin and Karla Kerlikowske, MD, of the University of California, San Francisco, used computer models to evaluate the risks and benefits of various screening schedules.

They found that in both cases, every-other-year screenings for women 50 to 74 may not be the best option. According to their models, average-risk women with lower breast density can limit their mammograms to once every three years without putting themselves at increased risk. Less frequent mammograms could also reduce false-positives and unnecessary biopsies, they write.

For women with high density breasts, the researchers found the opposite: Because this group is at higher risk of cancer, they found that more frequent screenings—once a year—could potentially save lives.

Dr. Berg, who wrote the accompanying editorial, agrees that tailoring screening recommendations to different groups of people is important.

“As we make this move toward precision medicine, we are getting away from the one-size-fits-all model to a more nuanced approach,” she says. “We’re taking into account a woman’s own feelings about mammography and her own risk factors, and that’s a good thing.”

Women should consider their breast density—along with other known risk factors, such as their family history, the age of their first period, and the age at which they first had children—when they decide how often they should be screened for breast cancer, says Dr. Berg. (Dense breasts must be diagnosed by a radiologist via a mammogram; it’s not something you can tell by feel or size.) Having your period earlier in life is linked to a higher risk of breast cancer, as is having children later in life or not at all.

For women with dense breasts, she says the study’s suggestion for annual screenings “makes perfect sense.” However, she doesn’t recommend average-risk women switch to less frequent screenings until more research is done.

“If a woman has low breast density, I’d say stick with the current recommendation of every other year,” she says. “Then maybe as she gets older, as we get more data and we learn more, perhaps you could switch to every third year.”

Earlier this year, the USPSTF issued an "I" statement, which is a call for more research, about whether additional screenings might be helpful for women with dense breasts. (The evidence so far, it said, was unclear.) The group generally does not comment on individual studies such as this one, and referred to its Frequently Asked Questions page for more information on its current position.

“The Task Force hopes that in the future, there will be more evidence available to make a more definitive recommendation,” the website states. “Women with dense breasts should talk with their doctors to determine what is best for their individual health needs.”