The Risk of Breast Cancer after Estrogen and Estrogen–Progestin Replacement

Abstract
To examine the risk of breast cancer after non-contraceptive treatment with estrogen, we conducted a prospective study of 23,244 women 35 years of age or older who had had estrogen prescriptions filled in the Uppsala region of Sweden. During the follow-up period (mean, 5.7 years) breast cancer developed in 253 women.