The risk of false positives is always a factor in breast cancer screening, but until now there hasn't been any hard data to pin down the exact rate of false positives from mammography. A recent study published in the Annals of Internal Medicine aimed to find out, reports Katherine Hobson at the Wall Street Journal's Health blog. Researchers looked at data from 169,000 women who began breast cancer screening in their 40s or 50s, and analyzed how often women received a biopsy but did not have breast cancer. "About 60 percent of women receiving annual mammograms — whether they began screening in their 40s or 50s — were recalled for additional imaging that showed a normal result over the first ten years of screening," Hobson says. "Some 7 percent of women who began screening in their 40s and 9 percent of women who started in their 50s had a mammographic finding that a biopsy showed to be a false positive." However, the researchers point out that women in their 40s will have a greater cumulative risk of false positive since they'll undergo more mammograms in total in their lives. "The risk of false-positive findings — both after further imaging and after a biopsy — was about a third lower in women who were screened every other year rather than annually," Hobson adds.
Screening: Yes or No?
Oct 20, 2011