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Screening women over 65 for breast cancer each year doesn't catch any more early tumours than screening every other year, but it does lead to more false positives, according to a US study.
The findings, which appeared in the Journal of the National Cancer Institute, are based on more than 140,000 older women included in five mammogram registries across the United States.
“Just having a false positive result means having the potential anxiety and inconvenience of having to undergo additional procedures,” said Dejana Braithwaite from the University of California, San Francisco, who led the study.
“This study clearly tells us that screening every two years may be more appropriate than screening women every year,” said Otis Brawley, chief medical officer of the American Cancer Society (ACS). However, he noted, there are other studies that suggest that annual mammograms are the way to go, even among older women.
Mammography guidelines from the ACS call for women to be screened for breast cancer every year, starting at age 40.
The US Preventive Services Task Force, on the other hand, recommends biennial screening for women ages 50 to 74, saying there's not enough evidence to recommend for or against mammograms for those aged 75 and older.
For the study, Braithwaite and her colleagues followed women aged 66 through 89 for seven years. During that time, about 3,000 were diagnosed with breast cancer and 138,000 remained cancer-free.
Among women with breast cancer, a similar proportion had invasive or advanced stage tumours, regardless of whether they had been screened every year or every other year leading up to their diagnosis. About two-thirds of those women were screened annually.
However, between 47 and 50 percent of women who were screened annually had a false positive mammogram at some point during the study period, compared to 26 to 30 percent of those screened biennially.
Braithwaite's team calculated that screening older women annually would result in almost four million additional false positives annually across the United States.
In older women in particular, biopsies and other procedures may worsen underlying health conditions, Braithwaite said.
“Our study shows that it really does very little benefit, in fact there is no benefit, with annual mammograms and there's this additional harm of having an increased probability of a false positive result,” she added. - Reuters