A new look at the science of preventing breast cancer deaths promises to reshape when and how many mammograms American women get — again.
One influential group plans to recommend that US women begin breast cancer screening mammograms at age 40 and continue to get them once every two years until age 75. This is expected to reduce the number of deaths from breast cancer by 19% compared with the previously approved mammography regimen.
The U.S. Preventive Services Task Force’s new list of draft recommendations marks a major shift from controversial advice promulgated in 2009 – and widely reiterated in 2016 – that most women could safely wait until age 50 to start to undergo a breast scan for signs of potential malignancies. The panel also said that women at medium risk could be screened every two years instead of every year.
Calling for fewer mammograms in a woman’s lifetime, the task force cited the frequency with which breast cancers are overdiagnosed, leading to invasive but unnecessary treatments, as well as the harm that comes from unnecessary biopsies and other tests. performed in response to false-positive test results. She also acknowledged that mammograms expose women to radiation, which in some cases could end up causing cancer in otherwise healthy women.
Those recommendations sparked a firestorm and were denounced by women’s health advocates, who have long argued that early detection offers the best chance of survival.
What made the task force change its mind and recommend that screening mammograms start at age 40? Members said they were greatly influenced by the experiences of black women, who tend to develop aggressive breast cancers earlier than white women and die from them more often. According to one study, black women are 39 percent more likely to die of breast cancer than the female population as a whole.
Screening black women early for breast cancer is only the first of many steps that need to be taken to address lingering gaps along ethnic lines. For Black, Hispanic, Latina, Asian, Native American and Alaska Native women, prompt follow-up and effective treatment for breast cancer will also be needed, experts warned.
Also driving the changes in the draft recommendations is a growing recognition of the risks faced by women with dense breasts, which make malignancies more common and harder to detect on mammography images.
Nearly half of all women have dense breasts, and task force members said they have little research to guide them on whether to recommend additional screenings or other types of imaging, such as MRIs or ultrasounds.
“New, more inclusive science on breast cancer in people younger than 50 has allowed us to expand on our previous recommendation and encourage all women to be screened every two years starting at age 40,” said Dr. Carol Mangione, chief of internal medicine at UCLA and the chair of the group that wrote the task force’s proposed recommendation. The new guidelines “will help save lives and prevent more women from dying from breast cancer,” she added.
Dr. Patricia Ganz, a breast cancer expert at UCLA who has served on many cancer screening teams, said there is little new evidence guiding the task force’s shift. But she called the group’s focus on addressing racial inequities in breast cancer “very, very important.” And she said the biennial mammography program is in line with practices in Canada and Europe.
“I think this is a great recommendation. It leaves doctors and their patients a lot of flexibility” in deciding how aggressive or relaxed their breast cancer screening should be, Ganz said. “The fact that they recommend starting at 40 means these women will soon have the opportunity to engage in a process of calculating their own personal risks.”
In doing so, women find themselves subject to a variety of breast cancer screening recommendations.
The American Cancer Society suggests that women begin annual mammograms at age 45, then consider switching to biannual testing at age 55. Women who would prefer to start annual screenings at age 40 can do so and should continue to get mammograms until they expect to live at least another 10 years, the ACS adds.
The American College of Radiology and the Society of Breast Imaging recommend annual mammography screening for all women age 40 and older who are at average risk of breast cancer.
Neither group suggests that 75 should be an upper limit for screening mammograms. But the American College of Radiology has recommended that all women have a breast cancer risk assessment by age 25 and discuss with their doctor whether early screening with mammography and/or MRI is needed.
Massachusetts General Hospital radiologist Dr. Debra L. Monticciolo was highly critical of the task force’s decision to recommend mammograms every two years, considering that black women and Jewish women die of breast cancer before age 50 – or even 40 – more often than white women as a whole. “This will only exacerbate racial disparities,” she warned.
“Their own evidence shows that the majority of lives are saved with annual screening,” said Monticiollo, who led the American College of Radiology/Society of Breast Imaging recommendations. “With the annual screening of women aged 40 to 79, there is a 42% reduction in mortality. Limit it to every two years and drop the mortality reduction to 30%. These are women’s lives that would be saved. I don’t know what their thinking is here.
However, the task force noted other consequences of switching from the less intense to the more intense screening program. The number of mammograms a typical woman received tripled, as did the number of false positive readings. The overdiagnosis rate has more than doubled, from 8% of cases to 17%.
Dr. Otis Brawley, a Johns Hopkins oncologist and cancer epidemiologist, said that while it seems counterintuitive that screening less often could save more lives, it’s a possibility that requires rigorous testing.
“Even many experts can’t come to grips with how many cancers are caused by mammography screening and how many deaths are diverted from that screening,” Brawley said. People who carry genes that predispose them to some cancers may be especially vulnerable to radiation-induced mutations, she said. “But this is not a trade-off that has been explored with strong research,” she added.
The task force made clear its new recommendations were not backed by solid confidence. The fact that women start getting mammograms in their 40s has had the strongest support from research. But the task force assigned much lower confidence values to its bi-yearly mammography schedule and to the idea that breast cancer detection after age 75 may not be life-saving.
“There is very limited research on this age population,” the panel’s report acknowledged.
The draft recommendation will be open for public comment until June 5. Comments can be submitted on the task force website.