Risk of breast cancer in relation to use of combined oral contraceptives near the age of menopause. WHO Collaborative Study of Neoplasia and Steroid Contraceptives.

Data from a multinational, hospital-based, case-control study were analyzed to determine whether use of combined oral contraceptives (OC) around the time of menopause preferentially increases risk of breast cancer. Results show that the relative risk (RR) of breast cancer was increased in women of all ages who had used oral contraceptives within the past year, but not to a greater extent in women near the age of menopause than in younger women. RRs did not increase with duration of OC use after age 45 in either pre- or postmenopausal women. RRs also were not found to be higher in women who were using OCs near the time of either a natural or artificial menopause than in women who used them at other times. This study thus provides no support for the hypothesis that OCs enhance risk of breast cancer by a greater amount when taken around the time of menopause than when taken at other times.