For years women have trekked to doctors’ offices for annual mammograms starting at age 40. But a new study says this may not be necessary: Women can wait until age 50 for their first mammogram with little downside, and they only need to get the exams every two years.
That’s the conclusion of guidelines issued today by the U.S. Preventive Services Task Force, a government-sponsored expert panel that evaluates preventive tests. Doing too many mammograms at too young an age generates colossal numbers of false positive results while only reducing breast cancer death slightly, according to new analyses commissioned by the USPSTF and published in the Annals of Internal Medicine. Previously, the USPTF had recommended mammograms every one to two years starting at age 40.
If the recommendations are broadly followed, it could reduce the number of mammograms a typical woman gets by half or more, threatening a multibillion-dollar industry. Roughly 37 million mammograms are done every year in the U.S. at a cost of around $100 each. Companies that make equipment for mammography include
The new screening recommendations were prompted by an exhaustive study of the practice to determine the best schedule to maximize benefits while minimizing harms. Among other things, the USPSTF commissioned six computer models to analyze detailed real-world data on benefits of regular mammograms starting at various ages with various time intervals.
Overall, they found that starting screening at age 40 instead of age 50 would save relatively few additional lives. To prevent one additional breast cancer death, 1,000 women would have to get mammograms starting at age 40 vs. age 50. But doing this would result in roughly 500 of the 1,000 women getting false positive results at least once, and 33 of them getting unnecessary biopsies, says Jeanne Mandelblatt of Georgetown University, who led one study combining the results of the computer models.
“Usually when we go to do something we want the benefits to outweigh the risks,” says UCSF primary care doctor Karla Kerlikowske, who wrote an editorial accompanying publication of the new guidelines in the Annals of Internal Medicine. “In this particular case [mammograms before age 50], it is kind of a tossup.” She says the new guidelines are based on solid evidence. “People should definitely embrace the new science.”
“This is not about saying ‘don’t be screened,’” says Diana Petitti, a doctor and preventive medicine expert at Arizona State University and vice chair of the USPSTF. “It is about saying ‘consider the tradeoffs and decide explicitly at which age to be screened.’” While some women may decide to get mammograms earlier than 50, she says, they should talk about the pros and cons first with their doctor and not just have it done automatically.
Organizations that support more aggressive screening, from the American Cancer Society to the American College of Radiology, immediately attacked the findings. “We respect the task force, but we do not agree with their conclusions,” says Leonard Lichtenfeld, deputy chief medical officer of the American Cancer Society. “We are concerned the same evidence we think supports beginning at age 40 is being interpreted by others as not supporting mammography.” He worries that the divergent recommendations will confuse women and make it harder for them to get coverage for mammograms.
“If cost-cutting U.S. Preventive Services Task Force (USPSTF) mammography recommendations are adopted as policy, two decades of decline in breast cancer mortality could be reversed and countless American women may die needlessly from breast cancer,” the American College of Radiology said in a statement.
Radiologist David Dershaw, who directs breast imaging for Memorial Sloan-Kettering Cancer Center, also thinks mammograms should start at age 40. “The bottom line for me is although mammography is not a perfect test it is the best thing we have,” he says. “There are multiple studies that show the ability of mammography to save lives is comparable for women in their 40s vs. women of older ages, and that when done annually it has the greatest impact.”
Dr. Kerlikowske counters that the new USPTF guidelines are based on a far more detailed and rigorous analysis of the mammography data than has ever been done before. (The USPSTF reviews its guidelines every five years.) “There is new evidence to precisely quantify benefits by age. It didn’t exist before,” says USPSTF’s Diana Petitti. “Those lines of evidence came together to a conclusion that the net benefit of starting earlier rather than later was small.”
The new guidelines come amid growing concern over whether American doctors, in their zeal to prevent disease, are conducting excessive numbers of tests in healthy younger patients, leading to false positive results and thus unnecessary treatment. (For more, see “Eight Tests That Could Save Your Life” and “ The Dark Side of Prostate Cancer Screening.”)
One problem with cancer screening is over-diagnosis. In essence, some tumors grow so slowly they will never kill you even if left untreated. Screening detects some of these tumors, resulting in many patients getting unnecessary treatment anyway with surgery and chemotherapy. Exactly how many women are treated unnecessarily for breast cancer as a result is unknown.
Meanwhile, mammography does a poor job of detecting fast-growing tumors that explode from nothing in just a few months. This is why even if you start screening at age 40, it only lowers the breast cancer death rate by around 20%.
Dr. Kerlikowske says that one reason why starting mammograms younger has only a modest effect is that younger women are more likely to get type of cancer called estrogen-receptor negative that grows faster and is hard to pick up on mammograms. Older women, on the other hand, are more likely to get estrogen-receptor positive tumors. These are picked up more easily by screening, she says.
In another counter-intuitive recommendation, the USPSTF says women don’t need to perform regular breast self-exams. These result in lots of extra doctor visits, but don’t slash the death rate from breast cancer, it says.