Effect of age and breast density on screening mammograms with false-positive findings.

OBJECTIVE: The objective of this study was to examine the effect of breast density and age on screening mammograms with false-positive findings. MATERIALS AND METHODS: The study sample was taken from the Washington State Mammography Tumor Registry, which links data from participating radiologists with the Puget Sound Cancer Surveillance System and the Washington State Cancer Registry. Participants (n = 73,247) were women 35 years old and older who underwent screening mammography for which an assessment and a four-category density rating were coded. A total of 46,340 mammograms were sampled to avoid interpreter bias. In this study of false-positive mammograms, only women with no diagnosis of breast cancer within 12 months of the index mammogram were included. Logistic regression was used to estimate the odds ratios of a false-positive mammogram being associated with each category of breast density or age, adjusting for the other factor as a covariate. RESULTS: After controlling for breast density, we found that the risk of a false-positive mammogram was not affected by age (p = 27). However, the trend of increasing risk of a false-positive mammogram with increasing breast density was highly significant (p < .001). Women with extremely dense breast tissue were almost two times more likely to have a false-positive mammogram than were women with fatty breast tissue. This effect persisted after controlling for age. CONCLUSION: Breast density, not age, is an important factor when predicting risk of a false-positive mammogram. Breast density should be considered when educating individual women on the risks and benefits of screening mammography.