A new 
study by researchers at Dartmouth College and the Oregon Health and Science University says that over the past 30 years more than 1 million women were diagnosed through mammograms with early stage breast cancers that would have not proved fatal if left undetected and untreated. The study concluded that these 1 million women were “overdiagnosed” and “overtreated.”
The authors of the study, which was published in the New England Journal of Medicine, concluded that mammography has done very little to save lives. They state that their results show “there is substantial overdiagnosis, accounting for nearly a third of all newly diagnosed breast cancers, and that screening is having, at best, only a small effect on the rate of death from breast cancer.”
The study cites previous research that found for every 10,000 women screened over a 10-year period, there will be five fewer deaths from breast cancer. But there will 50 cases where breast cancer is overdiagnosed.
The results are controversial and the American Cancer Society continues to suggest that women over 40 continue to have annual mammograms.
The article from the New England Journal of Medicine can be accessed here.