By David Olmos Nov. 16 (Bloomberg) — Annual mammograms are unnecessary for women in their 40s, and those in their 50s should only have them every two years, a panel of U.S. doctors said, drawing opposition from the American Cancer Society . The U.S. Preventive Service Task Force , a government-backed panel of doctors, said potential harm from annual screening, including false-positive results, cuts the test’s benefits. The panel’s recommendations, which do not cover women who carry a high risk for the disease, also urge that doctors stop showing women how to do self-examinations because there is little evidence it cuts cancer deaths. The new guidelines, published today in the Annals of Internal Medicine , pit the task force against the Cancer Society, which said doctors should still advise women to get routine annual screening starting at age 40. An estimated 64 percent of women age 40 to 49 have had an X-ray of their breasts during the past two years, the panel’s report said. “This is not a blanket recommendation not to worry until age 50,” said Diana Petitti , a disease epidemiologist at Arizona State University in Tempe, Arizona, and vice chair of the panel. “It’s a recommendation to have a discussion with your physician to better understand the trade-offs between starting exams now and starting later.” General Electric Co. , based in Fairfield, Connecticut, Eastman Kodak Co. , of Rochester, N.Y. and Munich-based Siemens AG , make imaging machines for mammograms and related supplies. Insurer Coverage J. Leonard Lichtenfeld , the American Cancer Society’s deputy chief medical officer, said such a recommendation may affect screening payments. ‘Our hope is that insurers will not make any change in coverage,” Lichtenfeld said. Wellpoint Inc. , the top U.S. health insurer by enrollment with 34 million members, pays for annual mammograms for women age 40 in the majority of its health plans. The Indianapolis- based company periodically reviews its reimbursement policies and “doesn’t adhere to any one source” for guidance, said Jill Becher, a company spokeswoman in Milwaukee. Mammograms, self-breast examinations and clinical examinations are the three main forms of detecting breast cancer. The x-rays are used to check for breast cancer in women who have no signs or symptoms of the disease, and also to check for breast cancer after a lump or other signs of cancer has been found, according to the National Cancer Institute . Breast cancer is the second-leading cause of death among U.S. women, after lung cancer, killing 40,480 women in 2008, according to the task force report. Computer Simulations The task force analyzed published research and developed computer-simulation models to evaluate the likely health outcomes if mammograms were begun at certain ages and done every year or two years. The study confirmed earlier research that women who have mammograms die less frequently of breast cancer than those who don’t have the tests. About two deaths per 1,000 women are averted if women begin annual screenings rather than exams every two years starting at age 40, the task-force estimated. It also estimated that women who begin getting mammograms at age 40 will have about 60 percent more false positive results per 1,000 exams than women who start screenings at age 50. A false positive, in which an abnormality is seen that proves not to be cancer, typically leads to additional screenings and tissue biopsies, the researchers said. “We are reluctant to recommend changing a proven program that has helped to save lives,” the Cancer Society’s Lichtenfeld said. The society questions whether the task’s force computer modeling “is sufficiently sophisticated and accurate enough,” he said. No Change in Policy Susan G. Komen for the Cure , the Dallas-based breast cancer advocacy group, also said it won’t change its recommendation that women ages 40-49 get annual mammograms. “We would not want to see a change in policy or reimbursement for screening mammography at this time,” said Eric Winer, the group’s chief scientific adviser, in a statement. Researchers and physicians have known for years that results from the x-rays are not as reliable in younger women as in older women. Women in their 40s typically have denser breast tissue, making it more difficult for technicians to determine if an image is normal or cancerous. After women enter menopause, typically at about age 50, the breast tissue becomes less dense and more fat, and the x-rays can be more accurately interpreted, said Susan Love , president and medical director of the Dr. Susan Love Research Foundation in Santa Monica, California. ‘Long Overdue’ The panel’s suggestions for women ages 40 to 49 are “long overdue,” said Love in a phone interview. “Most countries in the world do not do mammography screening until age 50.” “There is a lot of anxiety created when someone tells you that there is something that showed up in a test,” said Karla Kerlikowske, an epidemiologist at University of California at San Francisco Medical Center who wrote an editorial accompanying the task force report. Subsequent exams expose women to more radiation, and although biopsies are “low risk,” some patients develop infections or experience pain and bruises, she said. Screening women ages 50 to 74 every two years “achieves most of the benefit of annual screening with less harm,” the task force said. Now women in the older age group get a mammogram, on average, every 14 months, according to the report. ‘Biggest Concern’ In forming its guidelines, the task force’s “biggest concern” was that women would be confused by conflicting advice from health experts or wrongly interpret the panel’s message as a blanket recommendation for those ages 40 to 49 to not ever get screened, Pettiti said. Instead, decisions by women below age 50, and their doctors, should be based on “the risk for breast cancer and preferences about the benefits and harms” the task force wrote in the study. Although the recommendations are “very clear and thoughtful,” women are likely to be confused by the different advice of health experts, Kerlilowske said. She and other physicians said it may be difficult to persuade many women in their 40s who have been told by their doctors for years that annual screenings are beneficial to accept the panel’s recommendations. “The task force is saying you can get 70 percent of the benefit if you get a mammogram every two years compared with every year,” said Lichtenfeld, of the American Cancer Society. “There will be women who say, ‘I want 100 percent of the benefit’.” To contact the reporter on this story: David Olmos in San Francisco at dolmos@bloomberg.net .