The question seemed simple enough: Should women in their 40s be advised to get routine mammograms in the hopes of catching breast cancers while they are still small and, presumably, easier to treat? But the more an expert panel of doctors, nurses and preventive health specialists studied the data, the harder it was to come up with an answer.
Without screening, 3.5 out of every 1,000 women ages 40 to 49 will die of breast cancer in the next 10 years; regular mammography can reduce that number to 3. The panel calculated that to save one life among women in this age group, 1,900 women must be screened annually for 10 years. The other 1,899 women will receive no benefit from mammography over that period, though they will field 1,330 call-backs for reassessment and 665 breast biopsies, and eight of them will be diagnosed with cancers whose prognosis will not be altered by detection via mammogram — either because they would never become dangerous or because they are so aggressive that there's little to be done.
Ultimately, the U.S. Preventative Services Task Force decided in November 2009 that whether the benefits are worth the risks is a value judgment each woman should make for herself.
"When it comes down to values, that's when you want to put it in the hands of patients and their doctors," says task force member Ned Calonge, a physician who at the time was the chief medical officer of the Colorado Department of Public Health and Environment.
The panel wrestled with the language, finally deciding to recommend "against routine screening mammography" for women in their 40s. The intention was to emphasize the word "routine," but instead people focused on the word "against," and "no one got beyond that," Calonge says.
Confusion and outrage ensued. The American Cancer Society, Susan G. Komen for the Cure and the American Congress of Obstetricians and Gynecologists criticized the task force recommendations and continued to call for annual or biennial mammograms for women in their 40s, in line with the panel's guidelines from 2002. The National Breast Cancer Coalition and other organizations that stood by the task force faced fierce criticism, and task force members found themselves defending their decision before a congressional committee.
More than a year later, the dust is still settling. Three new studies examining the benefits of mammography have been released since the guidelines were revised, but they have only added to the confusion.
A study published last March in the journal BMJ compared women who lived in a region of Denmark where mammography screening was offered to those who lived in areas without screening and found no reduction in breast cancer deaths associated with mammography.
A similar study published in the journal Cancer in September compared breast cancer death rates in women from a region of Sweden with a public mammography program to those in an area without the program and found that deaths were 29% lower in the area with a screening program.
Yet another study that month, published in the New England Journal of Medicine, compared breast cancer deaths in women taking part in a Norwegian national screening program with those who were not screened, looking at mortality rates in those areas before and after the screening program began. This study found that breast cancer deaths had dropped since the mammography program began. But it calculated that most of the improvement was attributable to increased breast cancer awareness, which led women to seek treatment right away for any lumps or bumps they discovered, and new treatments. The contribution of routine mammography to the reduction may have been as small as 2%.
How could these studies yield such contradictory results? The answer is simple, says Dr. Heidi Nelson of Oregon Health and Science University in Portland, who led a research team that compiled evidence for the task force. All of these studies were observational, meaning they were done on groups of women who either chose to get mammograms or didn't — and there can be very real differences between those two groups.
"If you just look at the women who show up for mammography, you're looking at a biased sample of people," Nelson says: Women who choose to get mammograms are usually healthier and more health-conscious than those who skip the screenings. For this reason, the task force based its recommendations on the evidence from trials that took groups of women who were as similar as possible and randomly assigned them to either a screening or no-screening group.
"We had eight randomized trials. That's as good as it gets in our line of research," Nelson says.
When the researchers looked at these eight trials individually, none of them showed a benefit from mammography, Nelson says. It was only when the trial data were pooled that a benefit emerged — a 15% reduction in the risk of dying of breast cancer. Though that sounds "pretty respectable," she says, it's actually quite modest because the number of women who die of breast cancer in their 40s is tiny.
To some people, the main problem with the task force recommendations wasn't the lack of support for widespread mammography for women in their 40s but the lack of guidance about how doctors could explain the uncertain medical evidence to their patients and help them make an informed decision.
After all, if a group of experts who had the time to plow through mountains of studies couldn't come to a consensus about whether these women should have routine mammograms, how were women and their doctors supposed to make an evidence-based decision?
"What they said is, 'We're in the era of personalized care — go to your doctor and personalize your own care,'" says oncologist Marissa Weiss, founder of the advocacy group Breastcancer.org. "But the fact is, most doctors don't have the skills to do this."
Nor, she adds, do patients.
"To tell women to make an intelligent, informed decision about mammography is irresponsible," Weiss says. "None of us know enough to accurately assess risk and identify who does and does not benefit from mammography."
But the decision doesn't boil down to math, since both the benefits and the risks are modest, counters Dr. H. Gilbert Welch, an expert on cancer screening at the Dartmouth Institute for Health Policy and Clinical Practice in Lebanon, N.H., and author of "Overdiagnosed: Making People Sick in the Pursuit of Health."
"There's no algebra to solve it," he says. Instead, what matters is the value each woman places on the variables in the equation. "Some women will dismiss the harms as being trivial — and that's fine. Others will decide that the benefit is too rare and they don't want to go through the much larger risk of being medicalized and going through procedures they don't enjoy."
Shared decision-making may sound good in theory, but in practice it's not always popular, says Dr. Cheryl Iglesia, chairwoman of the American Congress of Obstetricians and Gynecologists' committee on gynecologic practice. "A lot of patients say, 'Well, doctor, I don't know what to do. You're the doctor. You tell me.'"
Iglesia, for one, simply fell back on the ACOG guidelines when dispensing advice to patients: These still call for annual or biennial mammograms for women in their 40s.
So what are women choosing? The journal Annals of Internal Medicine conducted an online poll last year about the new recommendations, and of the roughly 240 women who participated, 71% said they would continue to get regular mammograms in their 40s — even if their doctors recommended against them. Fewer than 20% planned to wait until age 50 for their first mammogram. While this poll does not reflect the thinking of women as a whole (since those with passionate feelings were probably more likely to respond), it does provide a snapshot of the continued struggle to make sense of the guidelines.
Of the more than 400 healthcare providers who also took the poll, slightly more than half said the recommendations would change how they advise their patients about breast cancer screening. Two-thirds said they would stop offering routine mammograms to women in their 40s.
Lost in the bickering over the guidelines for 40-somethings is the fact that there's widespread agreement about most everything else, says Dr. Otis W. Brawley, chief medical officer of the American Cancer Society.
"We all agree that mammography saves lives, we all agree on the magnitude of lives saved, and we all agree there are drawbacks and benefits," he says. While the debate about women in their 40s rages on, he adds, "nearly 20,000 women in their 50s and 60s die over a 10-year period because they don't get a mammogram, when we all agree they should."