Accuracy of breast screening among women with and without a family history of breast and/or ovarian cancer.

OBJECTIVES: To compare interval cancer rates, sensitivity and specificity of breast cancer screening between women with moderate or strong family history and women without a family history.
METHODS: From 1996 to 1997, 115,460 women aged 50 to 69 screened by the Ontario Breast Screening Program, offering eligible women screening with mammography and clinical breast examination, were examined. Women were followed for up to 12 months after their screening examination. Family history definitions were based on the number of affected first degree relatives and their ages at diagnosis. Multivariate analysis was conducted to adjust for potential confounding variables.
RESULTS: Interval cancer rates increased across family history groups and were greatest in women with a strong family history. The rate ratio (RR) for interval cancer rate in women with a strong family history compared to women without a family history approached significance (RR=2.28, 95% confidence interval (CI) 0.97-5.34), while for women with a moderate family history it did not (RR=1.37, 95% CI 0.62-3.04). A slightly but not significantly lower sensitivity was observed in women with a strong family history compared to women without a family history. There was little variation in specificity across family history groups.
CONCLUSIONS: Screening was able to detect a large proportion of invasive breast cancers in women with a family history, indicating their potential to benefit from regular breast cancer screening. However, due to increased interval cancer rates, screening with one-year intervals may be important even in an older population of women with a family history.