About 70,000 women are needlessly treated for breast cancer each year

New study revisits questions about benefits of routine mammograms

Over the last 30 years, more than 1.3 million women who were diagnosed with breast cancer through routine mammograms received unnecessary treatment for "abnormalities that otherwise would not have caused illness," according to a study by Dartmouth Institute for Health Policy & Clinical Practice researchers. 

For the study, published in NEJM, researchers used data from 1976 through 2008 to examine early-stage and late-stage breast cancer diagnoses among women age 40 and older.

About 70,000 women are over-diagnosed and treated unnecessarily for breast cancer each year, according to lead author Gilbert Welch of Dartmouth Medical School.

"[A]lthough no one can say with certainty which women are over-diagnosed, there is certainty about what happens to them," the study says. These women "undergo surgery, radiation therapy, hormonal therapy for five years or more, chemotherapy, or (usually) a combination of these treatments for abnormalities that otherwise would not have caused illness."

Moreover, the use of mammograms has not decreased the prevalence of metastatic breast cancer nor reduced the rate of breast cancer diagnosed in late stages, the study says. While fewer women are dying from breast cancer, it is because of better medications and treatments, not screenings, experts say.

"Women should recognize that our study does not answer the question, 'Should I be screened for breast cancer?' However, they can rest assured that the question has more than one right answer," the study says (Welch/Bleyer, NEJM, 11/22; Kearney, Medical News Today, 11/24; Knox," Shots," NPR, 11/21).

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