Oral contraceptives and benign breast disease: an update of findings in a large cohort study.

BACKGROUND: This report is an update of findings, first reported in 1981, on the relationship between oral contraceptives (OCs) and benign breast disease with special reference to OCs containing <50 mcg estrogen. STUDY
DESIGN: The Oxford-Family Planning Association study includes 17,032 women using different methods of contraception recruited at 17 family planning clinics between 1968 and 1974. These women were subsequently followed up until mid-1994. Among other items, information about contraceptive method changes and morbidity as measured by hospital referrals was collected during follow-up.
RESULTS: The findings in the present analysis were broadly similar to those reported in 1981, but based on much larger numbers of cases [fibroadenoma (FA), 185 cases; chronic cystic disease (CCD), 1361 cases; breast lump with no specific diagnosis (BL), 650 cases]. Hospital referral rates for FA and CCD (but not BL) declined with increasing duration of OC use, with the effect being strongest among recent users. The apparent protective effect was present for women using OCs containing >50 mcg, 50 mcg and <50 mcg estrogen but not for progestogen-only OCs.
CONCLUSION: Low-dose combined OCs containing <50 mcg estrogen appear to reduce the risk of hospitalization for FA and CCD as well as older preparations containing higher doses of estrogen.