Early age of onset in familial breast cancer. Genetic and cancer control implications.

Although breast carcinoma is the most frequently occurring cancer in American women and has been the subject of extensive epidemiologic investigation, little attention has been devoted to use of risk-factor information in its control. Six of our 52 breast-cancer-prone families have at least one woman who has manifested breast cancer at age 30 or earlier. One such family had two women with breast cancer before age 30, and at least ten others affected by age 50. Transmission of this lesion was consistent with autosomal-dominant mode of inheritance. Ages of onset indicated a notably early peak, in contrast with the expected pre- and post-menopausal peaks in findings of the New York State Tumor Resistry and others. Genetic and epidemiologic information should be utilized to control breast cancer in certain families.