In this Thursday, May 6, 2010 file photo, a radiologist uses a magnifying glass to check mammograms for breast cancer in Los Angeles. There's more disappointing evidence that breast cancer screening is not as helpful as many women believe. A big U.S. study shows that mammograms have done surprisingly little to catch deadly cancers before they spread. At the same time, they have led more than a million women to be treated for growths that never would have threatened their lives. (AP Photo/Damian Dovarganes, File)