Autosomal dominant inheritance of early‐onset breast cancer. Implications for risk prediction

Background. Improvements in screening techniques have made significant contributions to the early detection of breast cancer. Physicians thus face the task of providing appropriate screening schedules for their patients. One group for whom this is particularly important are those women with a family history of breast cancer. Methods. In this report, data from the Cancer and Steroid Hormone Study, a population‐based, case‐control study conducted by the Centers for Disease Control, are used to provide age‐specific risk estimates of breast cancer for women with a family history of breast cancer. The data set includes 4730 patients with histologically confirmed breast cancer age 20–54 years and 4688 control subjects who were frequency matched to patients by geographic region and 5‐year age intervals. The data set also includes family histories of breast cancer in mothers and sisters of both patients and control subjects. Results. Genetic models fit previously to these data by the authors have provided evidence for a rare autosomal dominant allele that results in increased susceptibility to breast cancer. In addition, these models predict that women who carry the allele are at greater risk of developing breast cancer at any age than are women who do not carry the allele. The increase in risk in carriers versus noncarriers does, however, decrease with increasing age. Based on the parameters of this model, age‐specific risks for a woman with one or more relatives affected with breast cancer at various ages at onset are given. Conclusions. These tables can be used for the purpose of counseling women at high risk of breast cancer development, that is, women with a family history of breast cancer.