Mammograms under the microscope
For some women, the screenings for breast cancer can do more harm than good.
What’s the debate over mammograms?
Major cancer organizations and women’s health groups have disagreed for years about whether widespread breast cancer screenings are helpful, as well as the best age for women to begin receiving them and how frequently. Proponents insist that mammograms, in which a woman’s breast is X-rayed to look for changes in the tissue, save lives by helping women detect breast cancer earlier, even before a lump is felt. More than 266,000 new cases of invasive breast cancer and nearly 41,000 deaths are expected in the United States this year, making it the second-leading cause of cancer deaths among women in the U.S., after lung cancer. But critics argue that routine testing may not be helpful for women younger than 45, and that the benefits might be outweighed by the harms, including false positives, which can lead to unnecessary biopsies, and the discovery and subsequent treatment of small, non-life-threatening cancers. Treating those issues can sometimes put women’s health in jeopardy.
How effective are the screenings?
The sensitivity of mammograms is about 87 percent, meaning the tests correctly identify 87 percent of women who truly have breast cancer. But studies have suggested the tests don’t result in significantly lower death rates, and that the value to younger, average-risk women is low. One of the largest mammography studies to date—a 25-year examination of 90,000 Canadian women ages 40 to 59—found no benefit for women who were randomly assigned to have mammograms over a group that received only breast exams done by nurses. The National Cancer Institute came to a similar finding about routine mammograms after analyzing multiple studies involving nearly 500,000 women, concluding that “screening for breast cancer does not affect overall mortality.” Moreover, many studies have concluded that overdiagnosis is a serious problem. A 2012 study in the New England Journal of Medicine found that mammograms overdiagnosed 1.3 million women in the U.S. over the past 30 years.
Why would overdiagnosis be harmful?
Mammograms can result in false positives or detect benign cancers that won’t ever become health threats during a woman’s lifetime. It remains difficult to tell harmless cancers from the ones that kill, so mass screening leads many healthy women to get unnecessary treatments, like invasive biopsies or even mastectomies. False positives also aren’t infrequent: after 10 yearly mammograms, the chance of having a false positive is about 50 to 60 percent. Many women experience anxiety and stress from being recalled for further exams and biopsies, not to mention a physical and financial toll. A 2013 study estimated that for every potential breast cancer death averted by mammography, an additional one to three deaths could be attributed to causes such as heart attacks that were linked to treatments women had received.
What do guidelines recommend?
The American Cancer Society suggests women undergo annual tests from 45 until 55—it had earlier recommended beginning at age 40—and then switch to every other year. The American College of Obstetricians and Gynecologists recommends that women begin annual screenings starting at 40. The United States Preventive Services Task Force, an independent panel of experts in evidence-based medicine, now recommends getting the tests every other year beginning at 50. Screening does reduce the odds of dying from breast cancer, the task force said, with women 60 to 69 benefiting the most. It estimates that screening 1,000 women from age 50 every two years for 24 years will avert seven deaths from breast cancer. But the tests could also lead to 953 false alarms and 19 overdiagnoses.
What advice are doctors following?
A recent study found that a full 81 percent of surveyed doctors continue to offer mammograms for women beginning at age 40. That may be because they have successfully treated patients in their 40s when a mammogram caught a serious case of breast cancer early, or it could be the fear of litigation or the fact that payment structures in U.S. health care reward the ordering of tests and procedures. Regardless of the difference in the experts’ guidelines, all major cancer groups recommend speaking to your doctor about your family history when you decide whether to get screened. If your mother or sister has had breast cancer, you may benefit more from mammograms than the average person; evidence shows that routine mammograms do reduce breast cancer deaths for women with a BRCA mutation. “We believe the benefits [of mammograms] increase with age,” said Dr. Michael LeFevre, who has led the U.S. Preventive Services Task Force. “But there are harms, and particularly in their 40s, women have to make a decision for themselves.”
The risks and benefits of prostate screenings
Prostate cancer will kill more than 29,000 American men this year, making it the second-leading cause of cancer deaths in U.S. men. The primary tool to detect it, the prostate-specific antigen (PSA) blood test, is controversial in the way mammograms are, because it can detect benign issues, leading to biopsies or more aggressive procedures. But last month, citing new data, the U.S. Preventive Services Task Force revised its stance on PSAs for men ages 55 to 69 from a “don’t do it” to a recommendation that patients make individual decisions after talking to their doctors. The group continued to recommend against screening for men 70 and over, saying the harms outweigh the benefits. ■