A new investigation of national Breast Cancer Surveillance Consortium data in the Annals of Internal Medicine reveals that, in one decade of yearly mammograms, over half of women without cancer will be called back for further testing, and approximately 1 in 12 women will be referred for a biopsy.

Investigation leader Rebecca Hubbard, PhD, an assistant researcher at Group Health Research Institute explained:

“We conducted this study to help women know what to expect when they get regular screening mammograms over the course of many years. We hope that if women know what to expect with screening, they’ll feel less anxiety if – or when – they are called back for more testing. In the vast majority of cases, this does not mean they have cancer. When a woman without breast cancer is called back after screening mammography for extra testing, she has a “false positive.”

We wanted to understand better how likely false-positive test results are when women receive annual screening mammograms compared to every other year – and starting at age 50 compared to age 40.”

Hubbard and her team analyzed data from over 169,000 women who were aged between 40 to 59 years across seven regions in the U.S..

According to Hubbard, women’s chances of having a false positive over the course of a decade was reduced from 61% to 42% when they were screen every other year, instead of annually. The probability of false positives was cut in half when women had previous mammograms available for comparison. Hubbard advises that women who don’t return to the same facility where they had their previous mammogram, should arrange ahead of time for their previous mammograms to be sent to the new mammography facility.

Hubbard continued:

“We found that women in their 40s and 50s had similar risks of having false positive during 10 years of screening. But over the course of a lifetime, starting screening at age 40 would make a women more likely to have a false positives than if she had started at age 50, because of that extra decade of screening.”

Their results revealed that women who were diagnosed with cancer from screening every other year were not considerably more likely to be diagnosed with late-stage cancer, compared to women who were screen annually. Hubbard explained: “Women should talk with their doctors to make informed decisions about how often is best for them to get screening – and when to start.”

Mammography is the only screening test to reduce the risk of a women dying of breast cancer that has been verified in clinical trials. For women who receive a false-positive it can be an extremely stressful experience, and may prevent women from getting regular screening.

In the same issue of Annals, an associated Breast Cancer Surveillance Consortium study led by Karla Kerlikowske, MD, of the University of California, San Francisco, is the first to examine the accuracy of digital mammography in comparison to film mammography in U.S. community practice. Newer digital mammography has been replacing older film mammography over the past few years.

The investigators, including Dr. Hubbard, discovered that both digital and film mammograms performed similarly for those aged between 50 to 79 years for detecting cancer. In addition they found that digital mammography might be better than film mammography in detecting cancer for women in their 40s with dense breasts, who had not gone through menopause. However, for women aged 40 to 49, the risk of having a false-positive was a little higher with digital mammography compared with film.

An associated report, from the International Prevention Research Institute in Lyon, France, puts the two investigations in context.

Both investigations were funded by The National Cancer Institute, which supports the Breast Cancer Surveillance Consortium. The collection of cancer data was also supported in part by several state public health departments and cancer registries across the United States.

As well as Drs. Kerlikowske and Hubbard, the additional co-authors of both investigations were Diana L. Miglioretti, PhD, of Group Health Research Institute and Bonnie C. Yankaskas, PhD, of the University of North Carolina at Chapel Hill.

In addition to Drs. Hubbard, Kerlikowske, Miglioretti, and Yankaskas, the other co-authors of the study on false positives were Weiwei Zhu, MS, of Group Health Research Institute and Chris I. Flowers, MD, of the Moffitt Cancer Center and Research Institute, in Tampa, FL.

And the other co-authors of the investigation on digital vs. film mammography were Constance D. Lehman, MD, PhD, of the University of Washington, also an affiliate investigator at Group Health Research Institute; Berta M. Geller, EdD, of the University of Vermont in Burlington; Stephen H. Taplin, MD, MPH, of the National Cancer Institute; and Edward A. Sickles, MD, of the University of California, San Francisco.

Written by Grace Rattue