CHICAGO, Nov. 27, 2012 /PRNewswire-USNewswire/ -- Researchers assessing the impact of revised guidelines for screening mammography issued by the U.S. Preventive Services Task Force (USPSTF) found evidence that the new recommendations may lead to missed cancers and a decline in screening, according to two studies presented today at the annual meeting of the Radiological Society of North America (RSNA). Routine screening mammography has traditionally been recommended by both the USPSTF and the American Cancer Society for all women over the age of 40. In 2009, the USPSTF issued controversial new guidelines recommending routine screening with mammography every two years for women 50 to 74 years old. In the studies being presented at RSNA 2012, researchers analyzed the impact of the new guidelines on women between the ages of 40 and 49 and the Medicare population. "Recommendations on screening mammography are extremely important public policy and we wanted to contribute to that dialogue," said Elizabeth Arleo, M.D., assistant professor of radiology at New York – Presbyterian Hospital — Weill Cornell Medical College in New York City. "We get questions all day long from patients and referring physicians on the appropriateness of screening mammography. The inconsistent information is very confusing for everyone." For her study, Dr. Arleo and a team of researchers analyzed data on screening mammography at New York – Presbyterian Hospital — Weill Cornell Medical College between 2007 and 2010. Over the four years, 43,351 screening exams were performed, which led to the detection of 205 breast cancers. "Nearly 20 percent of cancers detected with screening mammography were found among women in their 40s, Dr. Arleo said. "It seems unacceptable to potentially miss nearly 20 percent of the breast cancers we are identifying. This, in our view, would represent a substantial degree of under-diagnosis." Of the women screened in the study, 14,528, or 33.5 percent, were between the ages of 40 and 49. Of the 205 breast cancers detected, 39 (19 percent) were found in the 40-49 age group. Of those cancers, more than 50 percent (21 of 39) were invasive. Only three of the women between the ages of 40 and 49 diagnosed with cancer had a first-degree relative with pre-menopausal cancer.