How Often Should Women Get a Mammogram?
Reported November 23, 2009
(Ivanhoe Newswire) – Some researchers say a mammogram every two years achieves most of the benefits of annual screening, with less harm.
This was the unanimous consensus of six independent research groups. Researchers from CISNET, the Cancer Intervention and Surveillance Modeling Network, used independent models to examine 20 screening strategies with different starting and stopping ages and intervals.
“It’s reassuring that all CISNET modeling groups came to the same conclusion even when applying different models to these data,” lead author Jeanne S. Mandelblatt, MD, MPH, of Georgetown Lombardi Comprehensive Cancer Center, was quoted as saying. “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.”
The CISNET analysis showed that screening every other year maintained almost all of the benefit of annual screening with about half the number of false-positives. Compared with no screening, mammography screening every other year from ages 50 to 69 achieves a median reduction in breast cancer mortality of 16.5 percent over a lifetime. If screening is started at age 40 versus 50 and performed every other year, there is a median mortality reduction of 19.5 percent (an additional 1 woman per 1000), but an increase in false-positives, unnecessary biopsies, and anxiety.
Mandelblatt says the benefits of biennial screening are consistent with what is known about the breast cancer’s biology. In the majority of women, most tumors are slow growing and this proportion increases with age, so that there is little loss in survival benefit across the population for screening every year versus every other year. For women with aggressive, faster growing tumors, annual screening is not likely to make a difference in survival. For these women, different approaches may be needed.
While the model results confirmed that mammography saves lives, Mandelblatt explained that few women develop breast cancer in the age groups under 50, and screening younger women is accompanied by a large number of false-positive mammograms.
“We need more research to understand how to tailor screening by individual risk,” she said. “These modeling data represent an average finding regarding the population of women, so it can’t be emphasized enough that women need to talk to their health care provider for a screening program that is best for them.”
SOURCE: Annals of Internal Medicine, November 17, 2009
