Women who took oral contraceptives before 1975, and whose mother or sister had breast cancer between 1944 and 1952, have triple the likelihood of getting breast cancer as compared with similar women who didn’t take the pill, according to a study in the Oct. 11 Journal of the American Medical Association.
Daughters and sisters of women who had breast cancer a half-century ago and who have at least two other relatives with breast cancer were nearly five times as likely to get breast cancer if they took the pill than if they didn’t. If they had a mother or sister plus at least four other relatives with the disease, their risk jumped to 11-fold, says study coauthor Dawn M. Grabrick, an epidemiologist at the Mayo Clinic in Rochester, Minn.
However, the study also shows that nieces or granddaughters of those original breast cancer patients were no more likely to develop the cancer if they used oral contraceptives than if they didn’t. The average duration of pill use was about 7 years.
Manufacturers lowered the amount of hormone in oral contraceptives in the mid-1970s, a move that may have lowered cancer risk. The study didn’t include pill use after 1975.