© 2000 by Oxford University Press
Journal of the National Cancer Institute, Vol. 92, No. 20, 1625,
October 18, 2000
© 2000 Oxford University Press
MEMORANDUM FOR: Science Writers and Editors on the Journal Press List
Factors Identified That Can Lead to False-Positive Mammograms
October 12, 2000 (EMBARGOED FOR RELEASE 4 P.M. EST October 17)
Some women face a nearly 100% chance of having a false-positive result after nine screening mammograms for breast cancer.
Because a woman may have 30 or more screening mammograms over her lifetime, Cindy Christiansen, Ph.D., Boston University School of Public Health, and colleagues identified those characteristics of women and their radiologists that were the most powerful predictors of the cumulative risk of a false-positive mammogram. They found that chances of a false-positive reading increased with number of breast biopsies, family history of breast cancer, estrogen use, time between mammograms, no comparison with previous mammograms, and the radiologist’s tendency to call mammograms abnormal. Only increasing age was related to a decreasing chance of a false-positive test. These results are presented in the October 18 issue of the Journal of the National Cancer Institute.
Data on 2227 women aged 40 to 69 years who received from one to nine screening mammograms over a 10-year period at a large New England health maintenance organization were considered in this study. A mammogram was classified as positive if a radiologist recommended special follow-up (repeat physical examination, diagnostic mammography within 12 months, ultrasound examination, or biopsy) or if the results were indeterminate or aroused a suspicion of cancer. A positive mammogram was further classified as false positive if no breast cancer was diagnosed within 1 year.
Of 9747 screening mammograms, 6.5% were false positive, and 23.8% of the 2227 women experienced at least one false-positive result. After nine mammograms, the overall risk of a false-positive mammogram was 43.1%. For a woman with the highest risk variables, the estimated risk for a false-positive mammogram was 98.1% at the first mammogram and rose to essentially 100% for the ninth mammogram. A woman with lowest risk variables had estimated risks of a false positive mammogram of 0.7% at the first and 4.6% by the ninth mammogram.
Of the 93 radiologists who read mammograms in this study, 48 had false-positive percentages of 5% or less, 17 had percentages of more than 5% to 10%, and 28 had percentages of 10% or more. If a woman in the low-risk category had nine successive mammograms read by a radiologist in the low false-positive group, her chance of a false positive mammogram would be 4.6%; if they were read by a radiologist in the highest false-positive group, her chance of a false-positive mammogram rose to 54%.
The authors conclude that predicting the risk of false-positive mammograms may be an important way of educating women about screening and dealing with the occurrence of abnormal mammograms. They note that, if women understand their risk of false-positive mammograms, they might be less anxious when a mammogram requires special follow-up.
Contact: Rebecca Sullivan, Boston University, (617) 638-8491; fax: (617) 638-8044.
Note: This memo to reporters is from the Journal staff and is not an official release of the National Cancer Institute (NCI) or Oxford University Press (OUP) nor does it reflect NCI or OUP policy. In addition, unless otherwise stated, all articles and items published in the Journal reflect the individual views of the authors and not necessarily the official points of view held by NCI, any other component of the U.S. government, OUP, or the organizations with which the authors are affiliated. Neither NCI nor any other component of the U.S. government nor OUP assumes any responsibility for the completeness of the articles or other items or the accuracy of the conclusions reached therein.
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