Etiology of human breast cancer: a review.

Abstract

Literature on the risk factors for human breast cancer and specific etiologic hypotheses is reviewed. The risk of breast cancer has been found to increase with increasing age at the time of first delivery. The incidence of breast cancer increases with age though the rate of increase varies geographically and in some countries declines in later life. Early menarche and late menopause are associated with higher risk while surgically induced menopause reduces the risk. The rate of breast cancer is 5-6 times higher in North America and Northern Europe than in most areas of Africa and Asia. A history of benign breast disease and a familial history of breast cancer also increase the risk. Breast cancer has been associated with cancers of the ovary endometrium uterine corpus and the colon. The excretion of low levels of androgen metabolites have been related to an increased risk of breast cancer. The hypothesis that breast cancer risk is related to estrogen metabolism during the first few years after menarche is the hypothesis most compatible with all the major epidemiological features of the disease and is virtually the only acceptable explanation. The roles of exogenous estrogens prolactin and progesterone in the disease have yet to be evaluated in humans. Virus studies and the relationship of breast cancer risk to patterns of androgen and estrogen metabolism seem the most promising areas for research in the control of breast cancer.