Because breast cancer, like all other types of cancer, is primarily a disease of aging, your risk of developing the disease increases the older you get. As we age, our bodies lose some of their ability to repair small defects in cells as they divide and reproduce. A tiny replication error on the cellular level in your mid-40s can snowball into a breast tumor that you'll find during a routine mammogram several years later.
Although the risk continues to grow as we age, the prime time to be diagnosed with breast cancer is between the ages of 50 and 69, according to data from the American Cancer Society. Statistics compiled in the ACS report for 2017-2018, "Breast Cancer Facts and Figures" estimate that 56 percent of early stage breast cancers are diagnosed in patients between the ages of 50 and 69 years of age. With invasive breast cancers, 50 percent of them are diagnosed between 50 and 69. These figures are significantly greater than the 20 percent of early stage breast cancers that are diagnosed between ages 40 and 49. And just 15 percent of invasive cancers are found in patients in the 40 to 49 age bracket.
Breast cancer is one of the few cancers that we routinely screen for, and the guidelines have long recommended mammographic screening -- images made of the breasts at regular intervals to check for changes in the tissues that could signal cancer -- for women beginning at age 40 and continuing until age 74. However, in 2009, after looking at the vast amounts of data available from several large, epidemiological studies, the U.S. Preventive Services Task Force altered its recommended screening guidelines to say that women with an average risk of breast cancer -- those who don't have a particularly strong family history of the disease or a genetic mutation such as BRCA1 or BRCA2 -- should consider pushing back the commencement of screening to age 50 and have mammograms every other year instead of annually. The guidelines don't recommend screening past age 74. But why? If cancer is a disease of aging, shouldn't older women be screened just as regularly, if not more so, than younger women?
"There's nothing magical about age 74," says Dr. Debra Copit, director of breast imaging at Einstein Medical Center in Philadelphia. She says that number became the de facto endpoint for screening guidelines because that's the upper limit of the data that was available when the guidelines were developed. The data were derived from randomized controlled trials conducted in the late 1970s and early 1980s, Copit says, and "they decided to stop at age 74 because the life expectancy was much less back then. So that's where the 74 number comes from."
Further, many adults over the age of 74 have other diseases, conditions or comorbidities that may pose a more immediate risk to life than an early stage breast cancer would, says Dr. Rosemary Leeming, director of the comprehensive breast program at Geisinger Medical Center in Danville, Pennsylvania. "The older you get, the more things compete for mortality, meaning that even though the risk of breast cancer goes up with age, women start to die of other things." She says heart disease, lung disease and a range of other potential issues, also related to aging, can become a more immediate threat than that posed by a small tumor growing slowly in the breast.
Because of these factors, the USPSTF concludes that "the current evidence is insufficient to assess the benefits and harms of screening mammography in women 75 years and older."
The harms the USPSTF references could include false positives -- in which the test indicates cancer is present when it actually isn't. This can lead to both emotional harm and unnecessary surgery or other treatments that carry their own side effects and risks. There's also significant anxiety and fear that can surround regular mammographic screening, something that Copit and her team investigated in a recent study.
That study, which was presented at the annual meeting of the Radiological Society of North America last week, looked at how frequently women wanted to be screened. Copit says guideline-setting organizations cite potential harms and false positives as reasons for not recommending mammograms every year, but "as a woman and a breast imager, I found it somewhat paternalistic to approach guidelines with that attitude without really querying the very people it affected. I was curious," she says, so she and her team asked 731 women averaging 59 years old who'd undergone screening and diagnostic mammograms at Einstein Medical Center what they thought about screening frequency. Seventy-one percent of these patients said they preferred having annual mammograms rather than biannual ones and to begin them at age 40.
Copit says that for most of the study participants, the anxiety surrounding mammograms only increased if the gap between them was longer, and once the test was over, the anxiety subsided. "The vast majority of people felt that having a mammogram every other year would cause more anxiety rather than equal or less anxiety than an annual mammogram," she says.
For some patients, it seems having more frequent mammograms is preferable, but for some it's not. However, even though the guidelines don't recommend screening every year or in patients over the age of 74, that doesn't mean you can't continue screening if your individual situation warrants it. Depending on your health history, projected longevity and risk factors, you and your doctor may decide that continuing to screen after age 74 is a good idea. Leeming says the ACS's guidelines are "probably the most reasonable. What they say is that someone who's in good health and has a life expectancy of more than 10 years should probably think about screening."
Accurately determining life expectancy is more art than science, but both Leeming and Copit recommend taking a common-sense approach to screening by discussing how a cancer would be handled if it turns up and any other health issues the patient has when making a decision about whether to continue breast cancer screening after age 74. "On a practical level, we get accused in this business of finding excess cancers and finding these very early things that potentially may not be a problem," Leeming says. "So do you really want to find that in someone who's 75 or 80, when it really might not be a problem in their lifetime?" Those are the sort of questions patients should talk through with their doctors when determining whether continuing to have regular mammographic screening after age 74 is the right decision for them.
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For her part, Copit follows American College of Radiology guidelines and recommends that women begin annual screening at age 40 and continue for as long "as they're doing other, normal preventive things like going yearly to visit their family doctor and getting blood pressure tests."
She says mammography isn't perfect, but it's currently the best tool we have. "I acknowledge that mammography has limitations. I acknowledge that there are false positives," but she says mammography has improved, and the addition of 3D mammography, called tomosynthesis, is helping to bring down the number of false positives. "I think it'll continue to evolve, but I think it's the best test we have right now for most women, and I think it should be done starting at age 40 and continue yearly after that."
Elaine K. Howley is a freelance Health reporter at U.S. News. An award-winning writer specializing in health, fitness, sports and history, her work has appeared in numerous print and online publications, including AARP.org, espnW, SWIMMER magazine and Atlas Obscura. She's also a world-record holding marathon swimmer with a passion for animals and beer. Contact her via her website: elainekhowley.com.