Oral contraceptives and breast disease
McGonigle, K.F.; Huggins, G.R.
Fertility and Sterility 56(5): 799-819
1991
ISSN/ISBN: 0015-0282 PMID: 1936311 DOI: 10.1016/s0015-0282(16)54647-0Document Number: 556579
This review covers the epidemiology of benign and neoplastic breast disease, the theoretical effects of steroids on the breast, and the effects of oral contraceptives on both. Breast cancer has been increasing since the 1940s in older U.S. women, killing about 44,500 of the 175,000 new cases per year. In addition fibrocystic breast disease may affect up to 50% of premenopausal women, resulting in 500,000 biopsies, of which 10% are cancerous, 33% of those in post-menopausal women. The involvement of steroids in development of the human breast, and in breast cancer, is reviewed. The breast does not complete its development until the end of the 1st pregnancy. The terminal ductal cells, from which breast cancers form, are susceptible to stimulation by progestins in nulliparas. Progestins, at least in the high doses used in early orals, protect against benign breast disease. Inadequate amounts of progesterone, however, as in irregular cycles, seem to predispose to breast cancer. Epidemiologic studies of oral contraceptive use and breast cancer are reviewed under the studies of oral contraceptive use and breast cancer are reviewed under the headings of overall results, age, age 45, parity, use before 1st pregnancy, use at young ages, latent effect, hormone formulation, associated benign breast disease, association with other neoplasms, and receptor status. There are slightly increased risks for cancer before age 45 for long-term use of pills before the 1st term pregnancy, although the data are not wholly consistent, in that the specific sub-groups of women affected differ in different studies. There is no clear evidence for a latent effect, that is, appearance of cancer 20-30 years after stopping the pill. Nor is there evidence of breast cancer linked to any specific pill type, nor with benign breast disease, nor with endometrial cancer. The reason for rising breast cancer rates is still unknown. The absolute number of increased cases related to oral contraceptives is insufficient to affect national rates. It is possible that the inconsistent findings in epidemiological studies reflects use of high-dose pills in the 1960s and early 1970s. The contraceptive and non-contraceptive benefits of the pill are more important for women's health than the potential cases of breast cancer in young women who took them for prolonged durations.