The combined effect of breast cancer risk factors.

An extension of the logistic model (Cox, 1970) is applied to the prospective study of breast cancer in Guernsey (Bulbrook and Hayward, 1967). Four important risk factors, age at menarche, family history, age at first birth and etiocholanolone excretion, are identified and shown to have additive effects on a logistic scale for the probability of developing breast cancer. The feasibility of screening a high risk group of women is considered and shown unlikely to be of practical value.