Breast Cancer from Oral and Transdermal Estradiol: A Cohort Study of Finnish Women

Evaluation of: Lyytinen H, Pukkala E, Ylikorkala O: Breast cancer risk in postmenopausal women using estrogen-only therapy. Obstet. Gynecol. 108(6), 1354–1360 (2006) [ 1 ]. A cohort study of 84,729 Finnish women over the age of 50 years who used oral or transdermal estradiol for at least 6 months, followed for the incidence of breast cancer using a national cancer registry. The study was conducted to evaluate whether the risk of breast cancer with estrogen-only therapy varies by dose, constituents or route of administration. A total of 2171 women developed breast cancer, with no increased risk observed for less than 5 years of use, and some risk for greater than 5 years of use for both oral and transdermal routes of administration.