Use of mammograms again under fire
Up to 70,000 American women annually are treated unnecessarily for breast cancer because they were screened with mammograms, according to an analysis in the New England Journal of Medicine released Thursday.
The issue likely will reignite a running debate over the value of cancer screening. The study is being challenged by cancer experts.
The study found that nearly one in three breast cancer patients — or 1.3 million women during the past three decades — have been treated for tumors that, although detectable with mammograms, never would have threatened their lives.
The report lays bare that perhaps the greatest risk of cancer screening — called “overdiagnosis” — has long been acknowledged by oncologists and even advocates of mammograms, but unknown to most women who undergo the procedures.
Overdiagnosis occurs when technology detects cancers that, although technically malignant, behave as if they're benign, says study co-author H. Gilbert Welch of The Dartmouth Institute for Health Policy and Clinical Practice in Lebanon, N.H. Though it may surprise the average patient, doctors have long known that some tumors aren't actually fatal. Instead, some remain dormant for years or even disappear on their own, doctors say.
Doctors and public-health campaigns typically emphasize the benefits of mammograms — such as the potential to detect cancers when they're smaller and more curable — but ignore the “huge human costs” of women who go through surgery, radiation and hormonal therapies for nothing, Welch says.
“We've suggested to women that having a mammogram is one of the most important things you can do for your health — and that's simply not true,” Welch said.
“I can't tell you the right thing to do, except to tell women the truth, tell them both sides of the story. We shouldn't be scaring women. This is a really close call.”
Many cancer survivors credit mammograms with saving their lives, a conviction that can help sustain them through painful treatments.
Authors acknowledge their study doesn't offer any guidance to women diagnosed with cancer. Because oncologists can't tell for sure which tumors are most dangerous, they treat all breast cancers — and even pre-cancers — as if they have the potential to kill, says co-author Archie Bleyer of St. Charles Health System in Bend, Ore.
Cancer advocates have mixed reactions to the analysis. Some say the authors overestimate the problem of unnecessary treatment.
In a statement, the American Cancer Society says “overdiagnosis is a matter deserving of attention,” but it notes that other analyses have arrived at different estimates of the number of patients treated unnecessarily.
Len Lichtenfeld, the society's deputy chief medical officer, urged people to view the findings “with caution.”
Overall, “the benefits of screening mammography outweigh the risks and harms, which are an unavoidable part of breast cancer screening,” Lichtenfeld says.