AIM: Biennial mammo has most of the benefits of annual screening

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Biennial mammography screening of average risk women between the ages of 50 and 74 accomplishes most of the benefits of annual screening with less risk of false-positive mammograms, unnecessary biopsies and over-diagnosis, according to a study by researchers from the Cancer Intervention and Surveillance Modeling Network (CISNET) published in the November edition of the Annals of Internal Medicine.

CISNET member and lead author of the study Jeanne S. Mandelblatt, MD, of Georgetown Lombardi Comprehensive Cancer Center in Washington, D.C., and colleagues found that the results of their study correspond to a unanimous consensus of six independent research groups representing a range of academic institutions.

The study examined 20 screening strategies by each of six independent research groups with different starting and stopping intervals and ages. All six independent groups confirmed that screening every other year maintains almost all of the benefit--81 percent--of yearly screening with nearly half the number of false-positive occurrences.

Most breast tumor growth is found to be slow in most women. Therefore, there is little loss in survival rates across the population for screening every year compared with every other year, according to Mandelblatt. In cases in which tumors are found to be fast-growing in women, annual screenings are not likely to increase survival rates, Mandelblatt said, and different treatment approaches may be necessary for these women. Additionally, beginning screening earlier than age 50 yields smaller benefits because fewer women develop breast cancer in those younger groups, while the number of false-positive mammograms increases, Mandelblatt said.

It was further found that if screening is begun at age 40, compared with age 50, and preformed every other year, there is a median mortality reduction of 19.5 percent, but an increase of false positives, unnecessary biopsies and anxiety. Compared with no screening however, mammography screening every other year from ages 50-69 attains a 16.5 percent median reduction in breast cancer mortality over a lifetime.

"While the findings represent a comprehensive review of existing data, decisions about the best screening strategy depend on individual and public health goals, resources and tolerance for false-positive mammograms, unnecessary biopsies and over-diagnosis," Mandelblatt said.

According to the authors, further investigation on this topic is ongoing.