Annual Mammography Not Needed
Women ages 40 to 49 years who have extremely dense breasts should be informed that annual mammography may minimize their risk of advanced-stage disease.
By Kristina Fiore, MedPage Today
Medically Reviewed byZalman S Agus, MD
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MONDAY, March 18, 2013 (MedPage Today) —Mammography every other year appears to be an effective breast cancer screening strategy for most women, researchers found.
Those ages 50 to 74 had a similar risk of advanced-stage cancer whether they had a mammography annually or every other year — regardless of breast density or hormone therapy use, Karla Kerlikowske, MD, of the San Francisco VA Medical Center, and colleagues reported inJAMA Internal Medicine.
The results were similar for women ages 40 to 49, except for those with extremely dense breasts: these women are more likely to have advanced-stage disease if they have biennial rather than annual screening, they reported.
"Biennial screening mammography for most women ages 40 to 49 and 50 to 74 years, even among those with high breast density or receiving combination hormone therapy, results in a similar risk of presenting with advanced-stage disease as annual screening mammography," they wrote.
Annual screening was also associated with higher rates of false-positives for all groups, something that women with extremely dense breasts will have to take into account when deciding on their screening schedules, they wrote.
"When deciding whether to undergo mammography, women ages 40 to 49 years who have extremely dense breasts should be informed that annual mammography may minimize their risk of advanced-stage disease, but the cumulative risk of false-positive results is high," they wrote.
The controversy over breast cancer screening has raged since 2009 when the U.S. Preventive Services Task Force (USPSTF) recommended against mammography for women in their 40s, along with biennial screening for those ages 50 to 74.
A number of studies have been published during that time have found mixed results as to the value of annual mammography, but most cancer and radiology societies have continued to push for yearly screening.
To determine the effect of multiple risk factors — age, breast density, and hormone therapy — on the risks and benefits of annual versus biennial screening, the researchers conducted a prospective cohort study of patients from community mammography centers in the Breast Cancer Surveillance Consortium between January 1994 and December 2008.
They had data on 11,474 women with breast cancer and 922,624 who didn't have the disease but had a mammography.
Overall, they found that having a mammogram every other year didn't increase the risk of being diagnosed with advanced stage disease, or having a large tumor size for women ages 50 to 74 — regardless of breast density or hormone therapy use.
Those with the combination of dense breasts and hormone therapy tended to have have an increased risk of advanced stage disease and large tumor size with biennial screening compared with annual screening, but it wasn't significant.
Also, there were no overall differences in this age group for triennial versus biennial screening.
For the majority of women ages 40 to 49, biennial and annual mammography had a similar risk of advanced stage disease. But for those with extremely dense breasts — about 12 percent to 15 percent of women in this age group — biennial screening carried an increased risk of both advanced stage disease and large tumor size.
"This benefit [of annual mammography] is counterbalanced by a higher risk of cumulative false-positive mammography results with annual screening," they wrote.
Indeed, the cumulative probability of a false-positive mammography after 10 years was highest among women ages 40 to 49 having annual screening if they had either heterogeneously dense breasts (68.9 percent) or extremely dense breasts (65.5 percent).
Cumulative false-positives were lowest for women ages 50 to 74 who had fatty breasts and were not on hormone therapy: 30.3 percent for annual, 17.4 percent with biennial, and 12.1 percent with triennial mammography.
"Notably, most women who undergo annual mammography are at high risk of false-positive mammography results and biopsy recommendations without added benefit from more frequent screening," they wrote.
Kerlikowske and colleagues said the results are consistent with other studies that show "minimal if any additional benefit" for annual mammography over biennial screening in women ages 50 to 74.
They noted, however, that the literature on women ages 40 to 49 is a little less clear.
These younger women "will need to decide if the added benefit is outweighed by the additional harms of annual screening and increased risk of false-positive mammography results and breast biopsy recommendations," they wrote.
Avice O'Connell, MD, chief of women's imaging at the University of Rochester Medical Center, who was not involved in the study, expressed caution about the findings.
"We need something better to find those late-stage cancers," O'Connell toldMedPage Today. "I would not say, don't bother with your mammogram,' because we're very good at finding early-stage cancers."
"I think women need to come every single year, but they need to be aware that it's not 100 percent, and there are cancers that don't show," she added.
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