A prominent medical group made a major change to its breast cancer screening guidance. Here's how to make sense of the new advice.

Mammograms are an effective way to screen for breast cancer, but it can be hard to determine when to start and when to stop screening.

By Catherine Roberts

Additional reporting by Daphne Yao

Most women should start receiving mammograms for breast cancer screening every other year beginning at age 40, according to new draft guidance released last week by the U.S. Preventive Services Task Force (USPSTF), an independent panel of medical experts that evaluates preventive medical services.

Previously the USPSTF had recommended that women start breast cancer screening at age 50. “Now, more inclusive science has shown us that all women should be screened for breast cancer every other year starting at age 40,” Carol Mangione, MD, immediate past chair of USPSTF said in a statement on the task force’s website. “Black women are 40 percent more likely to die from breast cancer than white women if they get it. They also are more likely to get more aggressive forms of breast cancer, so this recommendation is particularly critical for Black women.”

While the evidence regarding breast cancer screening’s effectiveness among women in their 40s hasn’t changed substantially between now and the last time the task force updated its mammography recommendations, other factors likely played a role in the change in guidance, says Ruth Etzioni, PhD, a cancer screening researcher and professor in the public health sciences division of the Fred Hutchinson Cancer Center in Seattle.

For example, some evidence suggests that newer mammography technology may be slightly more accurate in younger women (so less likely to lead to a false alarm). And the incidence of breast cancer among younger women, while still not high, is on the rise. (About 10 percent of breast cancer deaths are in women under 50, and the average age of diagnosis is 62.)

“Guidelines are not made in a vacuum,” Etzioni says. “They’re made in an environment of public sentiment, of scientific consensus, and changes in awareness of the threats and solutions for public health.”

The evidence that mammography prevents cancer deaths isn’t as strong for women in their 40s as it is for women in their 50s, says Otis Brawley, MD, a distinguished professor of oncology and epidemiology at Johns Hopkins University in Baltimore. Still, he says the change in the recommendation seems reasonable.

“I see a realization that we do not have a clinical trial that shows that screening saves lives for women aged 40 to 49; however, many of us, including myself, believe that it does,” Brawley says. He says the task force calls for more clinical research that could help clarify the benefits of screening in those women. “And they clearly say, until we have done that clinical research, especially with the rise in the death rate for women in their 40s, it is appropriate to do screening at this time,” he says.

Here’s what to know about this new guidance on breast cancer screening.

The Different Breast Cancer Screening Recommendations

Mammograms are the best way to find breast cancer for most women of screening age, according to the Centers for Disease Control and Prevention. But determining who actually needs a mammogram is not so straightforward. Cancer experts don’t fully agree on when women should begin to have this breast cancer screening test—which checks for changes in breast tissue that could signal cancer before symptoms appear—or how often to do so.

Along with the USPSTF, a number of prominent medical groups also make recommendations on breast cancer screening that differ in key ways. 

For instance, the American Cancer Society (ACS) recommends starting at 45, and the American College of Obstetricians and Gynecologists (ACOG) says women should start screening no later than age 50. But both say that women who want to start earlier, by age 40, should have the option. The American College of Radiology (ACR) advises beginning at age 40.

Why the different advice? In part, it’s because these expert groups may evaluate scientific studies on mammography differently, some placing more weight on the benefits of mammography and others emphasizing the screening’s potential downsides, according to the American College of Physicians (ACP).

The Benefits and Harms of Mammograms

Death rates from breast cancer have been decreasing for several decades, and evidence suggests that the introduction of breast cancer screening programs is partially responsible—along with the development of more effective treatments. 

“In the pre-chemotherapy era, most of the reduction in [breast cancer] mortality was attributable to screening,” says Barry S. Kramer, MD, former director of the National Cancer Institute Division of Cancer Prevention. Today, the main driver is improvements in cancer treatments, he says.

Still, evidence shows screening does save lives. The benefit is clearer in older women, in part because breast cancer becomes more common with age, so screening is likely to catch more cancers. Estimates vary as to how likely screening is to prevent a breast cancer death today.

The USPSTF’s analysis of randomized controlled trials found that screening 10,000 women ages 60 to 69 regularly for a decade led to 21 fewer women dying of breast cancer. For women ages 50 to 59, screening prevented about 8 deaths for every 10,000 women over a 10-year period. For women in their 40s, the task force analysis found that screening prevented three deaths for every 10,000 women screened for a decade. 

Those benefits must be weighed against potential harms. For example, more screening also means more potential false positives: findings on screening mammograms that suggest cancer but turn out to be benign. False alarms are most common in women in their 40s, and the risk of having one declines with age, in part because younger women tend to have denser breasts. Dense breast tissue makes mammograms more difficult to read. And while a false alarm is better than a cancer diagnosis, it’s often no small matter: Sometimes, a woman “gets called back 2 or 3 times, and gets biopsies, and waits to hear, and then is told there’s nothing,” Brawley says. “They get so frustrated with mammography, they just drop out of mammography altogether.”

Among 1,000 mammograms on women in their 40s, the USPSTF cited estimates that there will be 121 false positives. For 1,000 scans on women 60 to 69, there would be 80 false positives. 

Another drawback is that recommending an extra decade of getting mammograms exposes people to more doses of radiation from the screening test itself. That radiation itself can raise the risk of cancer. One modeling study suggested that out of 100,000 women being screened every year from ages 40 to 55, and every other year after that through age 74, 86 women would develop breast cancer due to radiation exposure and 11 would die from it. Brawley says this is one reason the task force likely chose to recommend screening every other year rather than every year.

Another possible harm is what’s known as overdiagnosis: the finding of cancers that will never go on to be life-threatening but are treated aggressively nonetheless. Part of the problem is that it can be difficult to tell which cancers are potentially deadly, and which will either never cause any problems or won’t progress fast enough to cause symptoms before a person dies for an unrelated reason.

Estimates of how often overdiagnosis occurs have varied widely. One of the more recent estimates, published in the journal Annals of Internal Medicine in 2022, concluded that about 1 in 7 cases of breast cancer found among women ages 50 to 74 who had a mammogram every other year are likely overdiagnosed.

Etzioni, an author of that study, says that overdiagnosis is generally less of a concern for women in their 40s, who may be newly evaluating whether to start getting mammograms earlier than age 50 in light of the new recommendation. For one thing, breast cancers diagnosed at younger ages tend to be more aggressive types, whereas breast cancers that appear in older women may be less aggressive. What that means is the older you are, the more likely it is that a cancer caught by a mammogram might not end up hurting you during your lifetime, Etzioni says. 

Furthermore, Brawley says that newer genomic testing technologies—used to analyze a cancer once it is found—are better able to predict how dangerous a breast cancer might be, so doctors can better customize the level of aggressiveness of a person’s treatment.

How to Discuss Breast Cancer Screening With Your Doctor

In light of the complexity of this issue, women and their doctors should use a process called shared decision-making, says Ana María López, MD, MPH, a past president of the American College of Physicians.

This means considering the harms and benefits of mammography, as well as your own preferences, and having a thorough discussion of your personal health background as well as your family’s health history.

The last two help your doctor give you an idea of your overall breast cancer risk. That’s essential because the various expert recommendations are only for women at average or slightly elevated risk. (Factors linked to a slightly higher risk of breast cancer include the use of hormone replacement therapy, menstrual periods that began before age 12 or continued after age 55, and a history of conditions such as dense breasts, obesity, smoking, and excessive alcohol consumption.)

If you’re at high risk—factors that may put you in that category can include a personal or strong family history of breast cancer, carrying a BRCA1 or BRCA2 genetic mutation, and a history of multiple chest X-rays or radiation treatments to the chest—you’ll need to follow a different screening plan than other women do. Your doctor can help you map it out.

The American Cancer Society, for example, offers guidelines for women whose lifetime risk of breast cancer is calculated to be about 20 percent or higher. (The average lifetime risk is about 13 percent, according to the National Cancer Institute.) These guidelines include receiving a breast MRI and mammogram yearly starting at age 30. You may even be eligible for clinical trials of new types of screening, López says.

Ultimately, it’s important to come up with some plan for screening with your doctor, because even among women ages 50 to 75, for whom the evidence in favor of mammography is strongest, a significant percentage of women don’t get any screening at all, Brawley says. 

Though most of the guidelines on breast cancer screening are specifically directed at cisgender women, many trans people may need mammograms as well. The UCSF Transgender Care Program recommends that beginning at age 50, trans women who have been on feminizing hormones for at least five to 10 years should receive mammograms every other year. Trans men or nonbinary people who have not had a mastectomy should follow the guidelines for cisgender women.

How to Make a Plan for Screening

Here’s a breakdown of what the updated guidance from U.S. Preventive Services Task Force (USPSTF) says about key breast cancer screening questions, plus what to know about advice from other expert groups, including the American Cancer Society (ACS), the American College of Obstetricians and Gynecologists (ACOG), the American College of Physicians (ACP), and the American College of Radiology (ACR).

1. When Should You Start Breast Cancer Screening?

What the USPSTF says: All women should start screening at age 40.

What else to consider: The ACP, in guidance from 2019 aimed at synthesizing the various existing screening guidelines, suggested that starting at 40 women should have the option to decide to start screening, and that screening should begin no later than 50. That’s similar to advice from both ACOG and ACS, while the ACR says to start at 40. “We certainly believe that the benefits of screening far outweigh any of the potential harms,” says Geraldine McGinty, MD, professor of radiology at Weill Cornell Medicine in New York City.

Keep in mind that the earlier you start screening, the more likely you are to have a false alarm.

2. How Often Should You Get a Mammogram?

What the USPSTF says: Screening should occur every other year.

What else to consider: The ACS says that screening should be done yearly starting at age 45, and every other year starting at age 55. The ACR recommends screening every year.

ACOG says that whether you have a screening mammogram every year or every two years should be a matter of preference, based on shared decision-making with your doctor. Keep in mind that the more frequently you get screened, the more likely you are to experience related harms.

3. When Should You Stop Getting Breast Cancer Screening?

What the USPSTF says: There’s not enough evidence to make a recommendation on whether screening should continue after age 75.

What else to consider: ACOG says women 75 and older should talk with their doctor about whether testing continues to make sense for them, while the ACS says anyone who expects to live at least 10 more years should continue screening.

4. What About Breast Exams?

The new USPSTF guidance doesn’t weigh in on the question of routine clinical breast exams. But overall, there’s little evidence that having your breasts checked by a physician reduces the risk of dying from breast cancer. Medical organizations generally don’t recommend this exam, though ACOG says it can be offered as an option every one to three years for women ages 25 to 29, and yearly for women 40 and older. 

You don’t need to regularly examine your own breasts, but being aware of how your body normally feels is a good idea. “I still think it’s important for women to have a general sense of the normal contour of their own breasts,” says Joann Elmore, MD, MPH, professor of medicine at the David Geffen School of Medicine at UCLA and director of the UCLA National Clinician Scholars Program. “Because a high proportion of breast cancers are still detected by the women themselves, not by screening.”

Editor’s Note: This article, originally published Oct. 25, 2021, has been updated to reflect the latest guidance on breast cancer screenings.

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