Oral contraceptives and breast neoplasia: a retrospective study.

Between 1 December 1968 and 31 December 1971 345 women aged 16-39 years with a lump in the breast (90 malignant and 255 benign) were interviewed at five London teaching hospitals together with 347 matched controls suffering from acute medical or surgical conditions or admitted to hospital for routine elective surgery. Questions were asked about each patient's medical, obstetric, menstrual, contraceptive, and social histories.The data do not suggest that the use of oral contraceptives is related in any way to the risk of breast cancer but provide some evidence that the preparations may actually protect against benign breast disease. This protective effect is largely confined to women who continue to use oral contraceptives and have used them altogether for more than two years. Such women appear to have only about 25% as great a risk of being admitted to hospital for a breast biopsy as women who have never used oral contraceptives at all.