Mammograms lead to overtreatment, do little to curb late-stage breast cancers, study concludes Washington Post·3 hours ago Mammograms have done surprisingly little to catch deadly breast cancers before they spread, a big U.S. study finds. At the same time, more than a million women… By Associated Press, Nov 21, 2012 10:18 PM EST AP Updated: Wednesday, November 21, 2:18 PM Mammograms have done surprisingly little to catch deadly breast cancers before they spread, a big U.S. study finds. At the same time, more than a million women have been treated for cancers that never would have threatened their lives, researchers estimate. Up to one-third of breast cancers, or 50,000 to 70,000 cases a year, don’t need treatment, the study suggests. It’s the most detailed look yet at overtreatment of breast cancer, and it adds fresh evidence that screening is not as helpful as many women believe. Mammograms are still worthwhile, because they do catch some deadly cancers and save lives, doctors stress. And some of them disagree with conclusions the new study reached. But it spotlights a reality that is tough for many Americans to accept: Some abnormalities that doctors call “cancer” are not a health threat or truly malignant. There is no good way to tell which ones are, so many women wind up getting treatments like surgery and chemotherapy that they don’t really need. Men have heard a similar message about PSA tests to screen for slow-growing prostate cancer, but it’s relatively new to the debate over breast cancer screening. We’re coming to learn that some cancers — many cancers, depending on the organ — weren’t destined to cause death,” said Dr. Barnett Kramer, a National Cancer Institute screening expert. However, “once a woman is diagnosed, it’s hard to say treatment is not necessary.” He had no role in the study, which was led by Dr. H. Gilbert Welch of Dartmouth Medical School and Dr. Archie Bleyer of St. Charles Health System and Oregon Health & Science University. Results are in Thursday’s New England Journal of Medicine. Breast cancer is the leading type of cancer and cause of cancer deaths in women worldwide. Nearly 1.4 million new cases are diagnosed each year. Other countries screen less aggressively than the U.S. does. In Britain, for example, mammograms are usually offered only every three years and a recent review there found similar signs of overtreatment. .