Background: Although it is recommended that women with a family history of breast cancer begin screening mammography at a younger age than average-risk women, few studies have evaluated the performance of mammography in this group.
Objective: To compare the performance of screening mammography in women with a first-degree family history of breast cancer and women of similar age without such history.
Setting: Mammography registries in California (n = 1), New Hampshire (n = 1), New Mexico (n = 1), Vermont [n = 1], Washington State n = 2), and Colorado (n = 1).
Participants: 389 533 women 30 to 69 years of age who were referred for screening mammography from April 1985 to November 1997.
Measurements: Risk factors for breast cancer; results of first screening examination captured for a woman by a registry; and any invasive cancer or ductal carcinoma in situ identified by linkage to a pathology database, the Surveillance, Epidemiology, and End Results program, or a state tumor registry.
Results: The number of cancer cases per 1000 examinations increased with age and was higher in women with a family history of breast cancer than in those without (3.2 vs. 1.6 for ages 30 to 39 years, 4.7 vs. 2.7 for ages 40 to 49 years, 6.6 vs. 4.6 for ages 50 to 59 years, and 9.3 vs. 6.9 for ages 60 to 69 years). The sensitivity of mammography increased significantly with age (P = 0.001 [chi-square test for trend]) in women with a family history and in those without (63.2% [95% CI, 41.5% to 84.8%] vs. 69.5% [CI, 57.7% to 81.2%] for ages 30 to 39 years, 70.2% [CI, 61.0% to 79.5%] vs. 77.5% [CI, 73.3% to 81.8%] for ages 40 to 49 years, 81.3% [CI, 73.3% to 89.3%] vs. 80.2% [CI, 76.5% to 83.9%] for ages 50 to 59 years, and 83.8% [CI, 76.8% to 90.9%] vs. 87.7% [CI, 84.8% to 90.7%] for ages 60 to 69 years). Sensitivity was similar for each decade of age regardless of family history. The positive predictive value of mammography was higher in women with a family history than in those without (3.7% vs. 2.9%; P = 0.001).
Conclusions: Cancer detection rates in women who had a first-degree relative with a history of breast cancer were similar to those in women a decade older without such a history. The sensitivity of screening mammography was influenced primarily by age.