Depending on when they received their last mammogram, women who receive a false-positive result are more or less likely to get screened at recommended intervals, according to preliminary findings from a University of North Carolina Comprehensive Cancer Center study. The findings (abstract #2585) will be presented at the American Association for Cancer Research Annual Meeting in New Orleans, Monday, April 18, 1-5 p.m., CST.
A false-positive result is when a mammogram finds something that looks like cancer, but it is later determined to be normal. A woman who undergoes annual breast cancer screening with mammography has, on average, a 61 percent chance of receiving a false-positive mammogram after 10 screenings, said Louise Henderson, PhD, a UNC Lineberger member and an assistant professor of radiology at the UNC School of Medicine, and the paper's senior author. For women screened every two years, the chance of a false-positive is 42 percent after 10 mammograms.
"False positives can cause anxiety and stress, and it often means additional costs and time off from work," Henderson said. "There is the potential for these factors to influence the subsequent screening behavior of women. It's important to remember that breast cancer screening works best when guidelines are followed and women get screened on schedule."
The Food and Drug Administration's Mammography Quality Standards Act and Program estimates that approximately 39 million mammography procedures are performed in the United States every year.
Previous studies have shown mixed results of whether women are adherent to screening guidelines after receiving a false-positive result, Henderson said.
In their study, researchers examined Carolina Mammography Registry screening data from 2004-2009 linked with private insurance data for 14,071 women aged 40 to 64 years.
The study drew on UNC Lineberger's Integrated Cancer Information Surveillance System (ICISS), a research tool that contains details on cancer cases across North Carolina, linked to health claims data for 5.5 million people insured by Medicare, Medicaid, State Employees' Health Insurance, and Blue Cross and Blue Shield of North Carolina.
They looked at whether women went on to get a mammogram within nine months to two years of receiving a false-positive result.
They found that 81.8 percent of women went on to get a mammogram within 24 months if they had a false-positive finding. That was compared to 84.2 percent of women who had a true negative result.
In terms of relative risk, women who received a false-positive result were 23 percent less likely than women who had a true-negative result to get another mammogram within two years if their prior mammogram was within one to three years of the false positive exam.
In contrast, women with a false-positive result who had their prior mammogram more than three years earlier were 80 percent more likely to have a screening mammogram within two years than women who received a true negative result.
"We found that a false-positive result may reduce the likelihood of a woman returning for her next planned screening mammogram if her prior mammogram was within 1 to 3 years," Henderson said. "But it may increase her likelihood to return if her most recent mammogram was more than 3 years prior."
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