False Positives Usually Just False Alarms

Mammography false positives should be expected

/ Author:  / Reviewed by: Joseph V. Madia, MD

(RxWiki News) There's nothing quite so frightening as being called back for another test following a mammogram. A new study shows that repeat screenings are not only common, but usually nothing to worry about.

If you're having annual mammograms, you should expect to be re-screened once every 10 years.  Your chances of being called for a second look are one in ten, while the odds of having a follow-up biopsy are one in 12.

"Relax. It's common to be called back for additional mammogram tests."

According to a recent study of the National Breast Cancer Surveillance Consortium, more than half of women - who do not have cancer - will be asked to return for re-screening at least once every decade. Rebecca Hubbard, Ph.D., an assistant investigator at Group Health Research Institute, designed the study to learn what women could expect during many years of having mammography. 

The study looked at the likelihood of false-positive test results for women having mammograms both annually and every other year. 

Here's what Hubbard and her colleagues found after reviewing the records of more than 169,000 women between the ages of 40 and 59.

  • Every-other-year screenings reduced false-positives by about a third - from 61 to 42 percent.
  • Having previous mammograms available for comparison cut the rate of false-positives in half.
  • Because of the additional time involved, women who begin mammography at age 40 are more likely to have false-positives than women who begin screenings at age 50.
  • Women who had mammograms once every two years were not significantly more likely to be diagnosed with late-stage breast cancers than women who had annual tests.

In an accompanying study which was published in the same issue of Annals of Internal Medicine, the Breast Cancer Surveillance Consortium study compared the effectiveness of digital and conventional film-based mammograms.

  • Both types of mammograms offered similarly accurate results for women ages 50 to 79.
  • Digital mammography may be more effective in detecting breast cancer in premenopausal women in their 40s who have dense breasts.

dailyRx asked Hubbard what she wanted women to take away from this study. "I would like women to know that being recalled for additional testing after participating in repeat screening mammography across many years is common, and that in the vast majority of cases this does not mean that a woman has cancer," Hubbard said.

"I hope that knowledge of the frequency of false-positive results helps women to feel less anxiety if and when they are recalled," she said.

"Women should be aware of the harms and benefits of different breast cancer screening strategies and should talk with their doctors about the screening schedule that best fits with their personal risk tolerance and breast cancer risk," Hubbard said.

These studies were published in the October, 2011 issue of  Annals of Internal Medicine.

Reviewed by: 
Review Date: 
October 18, 2011
Last Updated:
October 19, 2011