False-Positive Mammograms Are Low
Norwegian Study: 1 in 5 Women Over Age 50 Affected In 20 Years
Aug. 23, 2004 -- Almost all women deal with anxiety after having a mammogram. Many are concerned about the risk of being told their results are abnormal.
Researchers now estimate that about one in five women who start getting mammograms between age 50 and 51 will get false-positive results during the next 20 years of screening.
While acknowledging the stress that may come from a false-positive mammogram, the rate seems to be "acceptable," given mammography's benefits, write the researchers in the online edition of the journal CANCER.
Solveig Hofvind, MSc, and colleagues from the Cancer Registry of Norway studied data from the Norwegian Breast Cancer Screening Program.
In Norway, every woman aged 50-69 is sent a letter inviting her to get a mammogram every other year. More than 83,000 women take that opportunity to have a screening mammogram done; information from their tests is then entered into the Norwegian Breast Cancer Screening Program data base.
A screening mammogram is a test to detect breast cancer changes in women who have no obvious signs of breast cancer. Early detection of breast cancer improves survival and reduces the number of deaths from the cancer.
These screening tests can, however, result in a false-positive mammogram reading -- a mammogram read as having some abnormality when in fact no cancer is actual present. This has been reported to be one disadvantage of many breast cancer screening programs. These false positive results can cause significant distress to many women.
In this newly published study researchers estimate the risk of a false-positive mammogram during a 20-year period in women who have screening mammograms starting at age 50 or 51.
The vast majority of women who start getting mammograms in their early 50s never have that problem, according to the Norwegian study. They find that the rate of a false-positive test was 21%, or approximately one in five women.
Even fewer women, 1%-4%, would have additional procedures resulting from the false-positive screening mammogram. These additional procedures include needle biopsy or other more invasive surgical procedures.
Although all abnormal mammograms should be followed up with additional testing (a diagnostic mammogram, ultrasound, and/or biopsy), most abnormalities turn out not to be cancer.
About seven out of 10 recalled women in the study had a follow-up mammography or ultrasound.
Women should be told how much -- or little -- risk they may have of a false-positive mammogram, say the researchers, who call for further studies on the topic.
SOURCE: Hofvind, S. CANCER (online edition), Aug. 23, 2004.