Geographical variation in endocrine function and its relation to breast cancer incidence: some general considerations.

Abnormalities in endocrine function are not a determinant of risk of breast cancer within countries, and racial differences in this function do not explain geographical variation in risk. It is suggested that hormonal status is related to tumor growth rates and hence to age at diagnosis, recurrence rates after primary treatment, and survival. Such evidence as there is points in this direction, but it still remains to be finally established whether the disease runs a similar course in all countries when patients are standardised for factors known to affect prognosis.