Background: Few data have been published on mammography performance in women who are younger than 40 years.

Methods: We pooled data from six mammography registries across the United States from the Breast Cancer Surveillance Consortium. We included 117 738 women who were aged 18-39 years when they had their first screening or diagnostic mammogram during 1995-2005 and followed them for 1 year to determine accuracy of mammography assessment. We measured the recall rate for screening examinations and the sensitivity, specificity, positive predictive value, and cancer detection rate for all mammograms.

Results: For screening mammograms, no cancers were detected in 637 mammograms for women aged 18-24 years. For women aged 35-39 years who had the largest number of screening mammograms (n = 73 335) in this study, the recall rate was 12.7% (95% confidence interval [CI] = 12.4% to 12.9%), sensitivity was 76.1% (95% CI = 69.2% to 82.6%), specificity was 87.5% (95% CI = 87.2% to 87.7%), positive predictive value was 1.3% (95% CI = 1.1% to 1.5%), and cancer detection rate was 1.6 cancers per 1000 mammograms (95% CI = 1.3 to 1.9 cancers per 1000 mammograms). Most (67 468 [77.7%]) of the 86 871 women screened reported no family history of breast cancer. For diagnostic mammograms, the age-adjusted rates across all age groups were: sensitivity of 85.7% (95% CI = 82.7% to 88.7%), specificity of 88.8% (95% CI = 88.4% to 89.1%), positive predictive value of 14.6% (95% CI = 13.3% to 15.8%), and cancer detection rate of 14.3 cancers per 1000 mammograms (95% CI = 13.0 to 15.7 cancers per 1000 mammograms). Mammography performance, except for specificity, improved in the presence of a breast lump.

Conclusions: Younger women have very low breast cancer rates but after mammography experience high recall rates, high rates of additional imaging, and low cancer detection rates. We found no cancers in women younger than 25 years and poor performance for the large group of women aged 35-39 years. In a theoretical population of 10 000 women aged 35-39 years, 1266 women who are screened will receive further workup, with 16 cancers detected and 1250 women receiving a false-positive result.