Do False-Positive Mammograms Predict Cancer Risk?
In the newly published study, researchers from the University of Copenhagen examined data from a population-based mammography screening program in Denmark.
The analysis included 58,000 women who had mammograms in that country between 1991 and 2005.
A false-positive mammogram was associated with a 67% greater likelihood of eventually receiving a diagnosis of breast cancer.
Women Screened Later Had Lower Risk
But the increase in risk among women who had mammograms after the year 2000 was roughly half that of women screened in the mid-1990s, and it was not considered significant.
University of Copenhagen associate professor of epidemiology and researcher My von Euler-Chelpin, PhD, says this suggests that screenings before 2000 may have missed more existing cancers.
“False-positive results are common in women undergoing regular mammography and can be reduced by undergoing screening every other year rather than every year,” Dr. Karla Kerlikowske, a professor of epidemiology and biostatistics and co-author of the study, told ABCNews.com. “Women are likely to maximize their chance of benefiting from mammography and minimize the chance of harm by undergoing mammography every other year.”
Federal guidelines currently suggest that women older than 50 receive a mammogram once every two years. But that guideline clashes with recommendations from the American College of Obstetrics and Gynecology and the American Cancer Society– both organizations recommend women begin getting annual mammograms at 40 years old.
In the study, published in the Annals of Internal Medicine, researchers examined data from nearly 330,000 women between the ages of 40 and 79 taken from a database of mammogram registries throughout the U.S. The study found that for every 10,000 women 40 to 49 years old who was given digital mammograms, two more cases of cancer would be found for every 170 false-positives.
Study authors said results should help physicians make informed decisions about mammogram screenings and create personalized treatment plans for patients.
The study appears in the May issue of the Journal of the National Cancer Institute.
“After 2000 the breast cancer detection rate increased and false-positives decreased,” she tells WebMD. “But the fact that the increase in risk remained for many years after screening also suggests that the breast characteristics that lead to false-positives may be associated with increased [breast cancer] risk.”
She adds that more study is needed to confirm the association.
U.S. May Be Different, Expert Says
Even if the results are confirmed, it is not clear if the findings apply to women in the United States, Bernick says.
That is because far more women in the U.S. are called back for second-look screenings or biopsies after initial mammograms.