For years, experts widely agreed that mammograms beginning at age 40 provided the best way for early detection of breast cancer. But new guidelines released this week by an important federal task force recommend a drastic change and raise new questions about the benefits of testing and exams.

The panel says women don't need mammograms until they're 50 and then only every other year, not annually. The potential harm of annual testing outweighs the benefits, the panel found. It was the first breast-cancer reassessment since 2002 by the U.S. Preventive Services Task Force, which typically guides federal policy.

The guidelines could have a far-reaching impact in the national debate over health-care reform. About 39 million women undergo mammograms each year in the United States. Critics worry that the policy shift could be a major setback for health, if insurers eventually scale back mammogram coverage for women in their 40s.

Published in the journal Annals of Internal Medicine, the guidelines have puzzled cancer doctors and contradict what many women have been told previously.

"We're not saying women shouldn't get screened. Screening does save lives," said Diana Petitti, vice chairwoman of the task force. "But we are recommending against routine screening."

The panel said women should wait until their 50s to begin having a mammogram every two years, and continue that schedule until age 74. It also recommends against teaching women how to perform breast self-exams, saying they don't save lives.

The guidelines were immediately condemned by expert groups, including the American Cancer Society, and have sparked fierce debate about routine screenings.

The guidelines were hailed by some physicians, however, who say the new recommendations may help protect women from false-positive results that incorrectly signal cancer and could lead to unnecessary anxiety, biopsies, and invasive surgeries.

The deep divide in the medical community underscores the need for improved technology and more research about breast cancer - how to prevent, detect, and treat the disease.

Unfortunately, with the new guidelines there are no clear-cut answers for women to figure out when to undergo screening and how often. Many women are understandably confused by the mixed messages. But they should remember that the guidelines are just that - merely advice.

In fact, Kathleen Sebelius, the secretary of health and human services, says the independent task force's recommendation won't change federal policy.

Women should consider the new guidelines and their personal medical history while talking with their own doctors about how to best protect their health against a potentially deadly disease.

More than 192,000 new cases of breast cancer are expected this year in the United States, and 40,000 deaths. No one disputes that early detection remains the best tool to save lives.