Projecting Individualized Probabilities of Developing Breast Cancer for White Females Who Are Being Examined Annually

To assist in medical counseling, we present a method to estimate the chance that a woman with given age and risk factors will develop breast cancer over a specified interval. The risk factors used were age at menarche, age at first live birth, number of previous biopsies, and number of first-degree relatives with breast cancer. A model of relative risks for various combinations of these factors was developed from case-control data from the Breast Cancer Detection Demonstration Project (BCDDP). The model allowed for the fact that relative risks associated with previous breast biopsies were smaller for women aged 50 or more than for younger women. Thus, the proportional hazards assumption was relaxed to allow separate proportional hazards models for those under age 50 and for those of age 50 or more. The baseline age-specific hazard rate, which is the rate fo