 -- In a major shift, the American Cancer Society is now changing its recommendations regarding mammograms and is now advising women to get yearly mammograms starting at age 45 if they have an average risk of breast cancer.

Previously, the organization had recommended that women get yearly mammograms starting at age 40 to check for signs of breast cancer.

Its new recommendations, published today in the Journal of the American Medical Association, come after reviewing studies that have questioned the benefit of annual mammograms for women in their 40s. The tests have become controversial for young women because of concerns that annual mammograms starting at age 40 may have led to false positives, which potentially contributed to an increase in biopsies and other unnecessary procedures since younger women have more dense breast tissue.

Additionally, after looking at the evidence the researchers at the American Cancer Society found there was not good evidence showing that mortality rates were different in younger women who underwent more mammograms.

"Despite some face validity in the idea that younger women, who often have more aggressive cancers, might benefit from shorter screening intervals, the actual clinical effects and importance remain uncertain," Dr. Nancy Keating, professor of health care policy and medicine at Harvard Medical School and a physician at Brigham and Women’s Hospital, wrote in an editorial accompanying the new recommendations.

The guidelines recommend women with average risk of cancer have annual mammograms starting at age 45 and biennial mammograms starting at age 55. They also stopped recommending clinical breast exams for patients of any age. These recommendations are not for women who have an increased genetic risk for breast cancer, such as women with the BRCA mutation.

"About 85% of women in their 40s and 50s who die of breast cancer would have died regardless of mammography screening," Keating said in her editorial. "More sophisticated screening tests that confer a greater reduction in breast cancer mortality would likely decrease breast cancer mortality much more than expanding screening mammography for women in their 40s and 50s."

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