A Norwegian study estimates that a many as 25 percent of cases of invasive breast cancers diagnosed by mammography screening are cases of overdiagnosis. (Photo/NCI)

Doctors must tackle the problem of the overdiagnosis in breast cancer screening — UW expert

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The time has come for the medical community to tackle the problem of overdiagnosis in breast cancer screening, writes Dr. Joann Elmore, a professor of medicine at the University of Washington, in an editorial in the current issue of the  journal Annals of Internal Medicine, which she co-authored with Dr. Suzanne Fletcher of Harvard Medical School.

A Norwegian study estimates that a many as 25 percent of cases of invasive breast cancers diagnosed by mammography screening are cases of overdiagnosis. (Photo/NCI)

Overdiagnosis occurs when routine breast cancer screening discovers a cancer that would have never caused symptoms in a woman’s lifetime.

When this is the case, a woman might undergo the ordeal of surgery, radiation treatments and chemotherapy for a tumor that she otherwise would have never known she had.

Elmore and Fletcher’s editorial accompanies a study from Norway appearing in the same issue of the journal that estimates that between 15 percent to 25 percent of invasive cancers diagnosed by mammography screening in that country are cases of overdiagnosis.

The rate of overdiagnosis in the U.S. may be even higher, write Ellmore and Fletcher in their editorial, because women in the U.S. typically begin routine mammography earlier — at age 40 compared to age 50 in Norway — and are screened more often — every year in the U.S. compared to every other year in Norway.

In addition, compared to European radiologists U.S. radiologists are more likely to identify abnormalities that require additional imaging, they note, further increasing the likelihood that slower-growing, less aggressive tumors that would have never caused problems are diagnosed.

While “the exact extent of overdiagnosis can be debated,” Elmore and Fletcher write,”it is time to agree that any amount of overdiagnosis serious and and to start dealing with this issue now.”

“Mammographers, especially those in the United States, could help by considering changes in the threshold for calling a mammography feature abnormal,” they write, and by developing strategies that would allow them to follow abnormalities over time rather than recommending immediate biopsies.

The risk of overdiagnosis does not mean women should not have mammograms, Dr. Elmore told LocalHealthGuide in a telephone interview.

Mammograms remain the best studied tool for the early detection of breast cancer, she said, but physicians should still explain the risks of overdiagnosis to their patients.

Ultimately, what is needed is a way to tell which tumors are likely to grow rapidly and need to be treated and which are likely to grow slowly or not at all and can be safely watched, Ellmore and Fletcher write.

Right now, no such test exists.

In the meantime, physicians have an ethical responsibility to inform women that there is a real risk that screening will lead to the discover of an abnormality that might never have caused them trouble, they write.

Currently, most patient-education materials do not even mention the risks and implications of overdiagnosis, they note.

Explaining these risks and implications will be difficult and if not done correctly may leave women “fearful or angry,” they write.

But, they add, “Just because communicating with patients will be difficult does not mean that we should not tackle this problem. Informed women deserve no less when deciding about breast cancer screening.”

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