Mammography screening has been shown to reduce deaths from breast cancer, but controversy remains about the best time to begin screening and how often to get screened. In 2009, the U.S. Preventative Services Task Force recommended that the decision to start regular mammography before the age of 50 years should be an individual one and that physicians should take patient context into account, including the patient's values regarding specific benefits and harms.

The Task Force also recommended that women aged 50 to 74 years and younger women who opted for screening should have screening once every two years versus every year.

A potential harm of shorter interval breast cancer screening is the risk of false-positive results. To compare the cumulative probability of false-positive results and stage of cancer diagnosis after 10 years of screening with either an annual or a biennial schedule, researchers studied seven mammography registries in the Breast Cancer Surveillance Consortium, the most comprehensive breast cancer registry in the world.

The researchers concluded that after 10 years of annual screening, more than half of women will have at least one false-positive recall, and 7 to 9 percent will have a false-positive biopsy recommendation. Biennial screening reduces false-positive recalls by about one-third, but is associated with a small increase in the probability of late-stage cancer diagnosis.

Using data from the same registry, researchers studied screening records for women aged 40 to 79 who underwent digital (n=213,034) versus film-screen mammography (n=638,252) to determine if one method was better than the other at detecting cancer.

The researchers found that digital and film-screen mammography were equally effective for women age 50 to 79, but for women age 40 to 49—especially those with dense breasts—digital was a bit more likely to find a cancer. However there was also had an increased risk for false positive results for these younger women.

"We conducted these studies to help women understand that having a false positive result is part of the process for mammography screening," said Rebecca Hubbard, PhD, Assistant Investigator at Group Health Center for Health Studies, Seattle, WA, and co-author of both studies. "We hope that by helping women know what to expect in terms of false-positive results, they'll be less likely to experience anxiety when they are called back for a repeat screening or biopsy."

The study authors recommend that women and their doctors develop a screening plan based on the patient's individual risk factors for breast cancer, and tolerance for false-positive recalls.

Source: Annals of Internal Medicine