Familial risks, early-onset breast cancer, and BRCA1 and BRCA2 germline mutations

Abstract

Background: Having a family history of breast cancer, particularly if it involves early-onset disease, is a risk factor for breast cancer, but little is known about specific causes of this association. Consequently, we studied mothers, sisters, and aunts of an age-stratified sample of 1567 unselected case patients diagnosed with breast cancer before age 60 years, recruited to a population-based, case-control-family study, in which case patients, control subjects, and their relatives were administered the same questionnaire. Methods: Extensive BRCA1 and BRCA2 mutation testing was carried out for 788 case patients diagnosed before age 40 years, including manual sequencing of DNA from 72 patien..