When to Get a Mammogram
Expert groups often disagree with each other on breast cancer screening. CR makes sense of the different recommendations.
By Catherine Roberts
Every October marks Breast Cancer Awareness Month, which always brings a flurry of reminders to women to stay up to date with their mammograms: X-rays that help detect lesions in the breast that may signal cancer. After a period when—according to research by the Centers for Disease Control and Prevention—many people appeared to delay their routine screenings because of the COVID-19 pandemic, these reminders may feel particularly urgent.
But determining who actually needs a mammogram is not so straightforward. Cancer experts don’t agree on when women should begin to have this breast cancer screening test, or how often to do so.
For instance, the U.S. Preventive Services Task Force (USPSTF), an independent panel of medical experts that evaluates preventive medical services, says women at average breast cancer risk should start screenings at age 50.
But the American Cancer Society (ACS) recommends starting at 45, and the American College of Radiology (ACR) advises beginning at age 40.
And the American College of Obstetricians and Gynecologists (ACOG) says women should start screening no later than age 50 but with the choice to begin sooner.
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 some emphasizing the screening’s potential downsides, according to the American College of Physicians (ACP).
They may also differ in the types of studies they rely on or on how to grapple with issues of cost when writing screening recommendations.
The result: “Both patients and clinicians are frustrated and sometimes confused,” says Joann Elmore, MD, MPH, professor of medicine at the David Geffen School of Medicine at UCLA and director for the UCLA National Clinician Scholars Program.
In addition, like all screening tests, mammograms themselves have their pros and cons.
Here, what to know about mammography, what the various recommendations may mean for you, and how to work with your doctor to make the best decision for yourself.
Understanding Testing's Benefits and Harms
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.
For instance, a 2018 study on Swedish cancer patients, published in the journal Cancer, found that women who participated in a screening program were less likely to die of breast cancer than women who skipped screening. However, women who choose to get screened may be more healthy in general than women who choose not to get screened, says Barry S. Kramer, MD, MPH, a consultant to the National Cancer Institute Division of Cancer Control and Population Sciences and former director of the NCI Division of Cancer Prevention.
And some experts think another factor is more significant in the fall of breast cancer deaths. “In the pre-chemotherapy era, most of the reduction in [breast cancer] mortality was attributable to screening,” Kramer says. Today, the main driver is improvements in cancer treatments, he says.
Estimates vary as to how likely screening is to prevent a breast cancer death today, but 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.
And breast cancer screening can carry harms along with benefits. One is the possibility for false positives, or findings that suggest cancer but turn out to be benign. (Mammograms may also, but more rarely, lead to false negatives—a missed cancer.)
According to the USPSTF, among 10,000 women 60 to 69 years old, 808 will receive a false positive result after one screening. A false positive can lead to anxiety and unnecessary follow-up testing, including biopsies, which are uncomfortable and carry a small risk of infection.
Another possible harm is overdiagnosis, the finding of cancers that will never go on to be life-threatening. Scientists don’t agree on how common this is, in part because it’s 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.
The USPSTF, which last addressed breast cancer screening in 2016, says that based on collected data from randomized controlled trials, about 1 in 5 breast cancers found may be overdiagnosed. Other studies used computer modeling to try and estimate the overdiagnosis rate, and these suggest that 1 in 8 breast tumors detected with mammography may be overdiagnosed.
A new study, published earlier this year in the Annals of Internal Medicine, employed more rigorous modeling techniques that the researchers say are aimed at accounting for some of the limitations of earlier studies of breast cancer overdiagnosis. They concluded that about 1 in 7 cases of breast cancer found among women ages 50 to 74 years who had a mammogram every other year are likely overdiagnosed.
Certain people may be at greater risk for some screening harms than others. For example, if you’ve been told you have dense breasts, you’re more likely than others to experience a false negative, false positive, or unnecessary breast biopsy, according to the USPSTF. Getting screened at younger ages, such as in your 40s, also makes you more likely to receive a false positive.
What to Discuss With Your Doctor
So, what should you do? 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 ACP.
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.
For women at average or slightly elevated risk of breast cancer, the ACP released guidance in 2019 that synthesizes the different sets of recommendations into a few simple pieces of advice. To create the guidelines, the organization evaluated and scored each set of advice, using criteria such as the rigor of the science involved in their development, clarity, and lack of conflicts of interest among its authors.
You can use the ACP’s guidance during a discussion with your doctor, and to help you answer the four key questions below.
1. When Should You Start Screening?
What the ACP guidance says: Women ages 40 to 49 should have the option for breast cancer screening, and doctors should discuss the harms and benefits of screening during these years. Healthcare providers should offer screening to women starting at age 50.
What else to consider: Age is the most important risk factor for breast cancer for most women, and the greatest benefits from screening are seen in women in their 60s, according to the USPSTF. Starting screening at age 50 is when the growing risk of breast cancer likely outweighs the risks of screening, the task force and the ACP say.
Still, the advice here varies. The ACS recommends beginning screening at age 45, 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, a past chair of the board of chancellors for the ACR.
Keep in mind that the earlier you start screening, the more likely you are to have a false alarm.
2. How Often Should You Have a Mammogram?
What the ACP guidance says: Screening should be offered every other year from ages 50 to 74.
What else to consider: The ACP guidance is in line with that of the USPSTF, while 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 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?
What the ACP guidance says: There’s no need to screen women 75 and older, or those who have a life expectancy of 10 years or fewer.
What else to consider: The last time the USPSTF addressed this question, in 2016, it concluded there wasn’t enough evidence to make a definitive recommendation on breast cancer screening for people 75 and older. (The USPSTF is currently working on updating its breast cancer screening recommendations.) 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 10 more years should continue screening.
4. What About Breast Exams?
What the ACP guidance says: There’s no need for doctors to perform routine clinical breast exams.
What else to consider: There’s little evidence that having your breasts checked by a physician reduces the risk of dying from breast cancer. Major groups 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.
And 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,” Elmore says. “Because a high proportion of breast cancers are still detected by the women themselves, not by screening.”
Editor’s Note: This article has been updated to reflect the latest guidance on breast cancer screenings.
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