An increased risk of breast cancer for relatives of breast cancer patients has been demonstrated in many studies, and having a relative diagnosed with breast cancer at an early age is an indication for breast cancer screening. This indication has been derived from estimates based on data from cancer-prone families or from BRCA1/2 mutation families, and might be biased because BRCA1/2 mutations explain only a small proportion of the familial clustering of breast cancer. The aim of the current study was to determine the predictive value of a family history of cancer with regard to early onset of female breast cancer in a population based setting.
The team followed an unselected sample of 1987 women with and without breast cancer to determine the age at which they developed breast cancer. The risk of early onset breast cancer was increased when there were at least two cases of female breast cancer in first-degree relatives, at least two cases of female breast cancer in first or second-degree relatives under the age of 50, at least one case of breast cancer in a first or second-degree relative under the age of 40 and any case of bilateral breast cancer. The positive predictive value of having 2 or more of these characteristics was 13% for breast cancer before the age of 70, 11% for breast cancer before the age of 50, and 1% for breast cancer before the age of 30.
The conclusion is that applying family history criteria in an unselected population could result in unecessary early screening of many women who had little risk of developing breast cancer at an early age.
