Since 2009, when the U.S. Preventive Services Task Force threw a grenade into the “mammograms for everyone” approach to women’s care, researchers, doctors and women have been wondering just who should get a mammogram, when and how frequently.
As widely reported last week, the results of new studies are helping to tease out the variables in this equation. Thanks to a greater appreciation that more tests don’t necessarily render better care, and that such overuse can cause patient harm, people are learning that customized medicine is superior medicine.
As the Los Angeles Times noted, “Of the various recommendations put forth by the U.S. Preventive Services Task Force in 2009, none generated more ire than the suggestion that annual mammograms could do more harm than good for most fortysomething women, who are far less likely than older women to get breast cancer….
“The new research was designed to identify women who could benefit the most from having mammograms early and often.”
The task force, an independent panel of health experts which advises the federal government, suggested more than two years ago that women older than 50 should have a mammogram every two years instead of annually, and that most women in their 40s should bypass the test altogether. Until then, women over 40 routinely were advised to have a mammogram annually.
The new research found that among women 50 to 74, for every breast cancer death averted by screening, 146 women received a false-positive reading — a false alarm — on a mammogram. And for every year of life someone gained thanks to a mammogram’s early detection of breast cancer, 8.3 false positives led to unnecessary biopsies, weeks of worry and sometimes surgical complications.
Two markers stood out for researchers as indicators that a 40-year-old should have regular and more frequent mammograms: a woman whose mother or sister was diagnosed with breast cancer, and women with unusually dense breast tissue.
These people, the studies concluded, carry at least twice the average risk of developing breast cancer in their 40s. For such women, according to the study in the Annals of Internal Medicine, routine screening outweighs the risk of false alarms and unnecessary, often invasive and uncomfortable tests.
One of the studies combined and analyzed data from 61 previously published studies. The other employed computer models to predict the health outcomes of approximately 44,000 simulated women who had their first mammogram at 50. The simulation was revised to show their outcomes had they begun screenings at 40. Then it compared the rates of false alarms, breast cancer diagnoses and mortality in both groups.
For the younger group, researchers found that the only ones who stood to benefit to a similar degree were those whose breast cancer risk was roughly double the norm for their age group. Having a first-degree relative – a mother or sister – with a breast cancer diagnosis more than doubles a 40-year-old’s own risk of developing the disease. Two or more first-degree relatives with breast cancer bump up the risk nearly fourfold.
Increased risk also was seen in women whose breasts are composed of significantly more glandular than fat tissue. That also doubled the risk of breast cancer risk for someone in her 40s.
The confounding element here is that dense breasts make mammograms harder to read: Cancerous tumors aren’t as apparent within glandular tissue as they are within fat. Radiologists, who review mammograms, and doctors lack established standards to define and grade breast density.
Other risk factors identified in the new studies were:
- biopsies–women whose breast biopsies were benign have an 80 percent greater risk of getting cancer in their 40s;
- oral contraceptives-30 percent greater risk;
- never having given birth-25 percent;
- first child after 30-20 percent increased risk.
As we’ve discussed before, percentages of increased risk don’t necessarily convey an accurate picture. The commonly heard refrain that a woman’s risk of breast cancer is 1 in 8 is misleading. That’s a skewed metric that fails to consider not the risk at age 40, but the lifetime risk for a woman who lives to age 90. The real figure for young adults is more like 1 in 813.
The new studies, of course, help women understand if their risk is higher or lower than average.
As the whys and wherefores of mammograms evolve, women and their doctors should focus on two things: getting an accurate family history, and understanding their individual breast anatomy. The state of the art today makes those the drivers of when to begin and how often to get a mammogram.