For decades it mostly went unquestioned: Women without symptoms were advised
to undergo routine mammograms to assure they were cancer-free, with the idea
that detection of early-stage breast cancer would increase their chances of
But a controversial study recently published in the New England Journal of Medicine concludes that women without symptoms who undergo screening and are diagnosed with breast cancer may experience more harm than good.
The observational study analyzed national statistics on breast cancer screening and incidence and death rates for a 30-year period, and it found that advances in breast cancer treatment are far more responsible for the decline in deaths than screening.
The study concludes that 1.3 million women have been overdiagnosed with early-stage breast cancer -- which the study defines as "the detection of a cancer that otherwise was never going to appear." Despite having no symptoms, women may be subjected to unnecessary radiation and hormonal treatments and even mastectomies.
The study has received criticism and support.
The New York Times Well blog, "Ignoring the Science of Mammograms," written by David H. Newman, describes the findings as "a bold claim for an observational study."
"There are countless reasons why conclusions from such studies are commonly fraught with error," states Dr. Newman, an emergency room physician in New York City. "What if, for instance, the lion's share of advanced cancers occurred among women without access to screening mammograms -- a fact often not available in health statistics? Or what if mammography successfully prevented a major increase in advanced cancers, leaving the health statistics unchanged?"
A study author, H. Gilbert Welch, a professor of medicine at the Dartmouth Institute for Health Policy & Clinical Practice at Dartmouth University, said the controversy was expected, although he said some criticisms are laughable. "This is a hot potato," he said. "There is probably no diagnostic or screening test promoted as aggressively as mammography. There is nothing like it, and people have engaged in the process [of being screened]."
But he said the study makes clear that the benefit of screening "is much smaller than people have been led to believe, and the harms are considerably larger."
Benefits are outweighed, he said, by the study's conclusions that 1.3 million women in the past 30 years -- 70,000 in 2008 alone or 31 percent of all breast cancers diagnosed that year -- were overdiagnosed, leading to unnecessary mastectomies or radiation and hormone treatments.
Diagnostic mammography for women who have symptoms, including detected lumps in their breasts, is recommended, Dr. Welch said, noting the importance of taking action when a woman has clear symptoms of breast cancer. "There is no debate about mammography" for that purpose, he said.
"Treatment has gotten a lot better. The better the treatment, the less important it becomes to find the disease early," said Dr. Welch who teamed with Archie Bleyer, the medical advisor to the Cancer Treatment Center at St. Charles Medical Center in Bend, Ore., to do the study.
One irony, he said, is that women without symptoms who are screened, diagnosed with early-stage breast cancer, then undergo treatment for what
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