Oral Contraceptive Progestin and Estrogen Use and Increases in Breast, Ovarian, and Endometrial Cancers

To the Editor Michels and colleagues¹ claim that long past oral contraceptive (OC) use reduces the risk of ovarian and endometrial cancer. Carcinogenic effects of more recent exposures to menopausal progestin and/or estrogen hormone therapy (HT) are ignored. Among the entire sample of women aged 50 to 71 years (median age, 60 years), 118 144 (60%) formed a control reference group that included both never users and women who had taken OCs for less than 1 year. Only 10% of women took OCs for at least 10 years. A follow-up 11 years later found that 18 199 women had cancer: 61% breast cancer, 19% colorectal cancer, 13% endometrial cancer, and 7% ovarian cancer.¹