On Jul. 17, 2002, A National Cancer Institute funded trial showed that postmenopausal women who used estrogen replacement therapy for 10 or more years were at significantly higher risk of developing ovarian cancer than women who never used hormone replacement therapy.

The relative risk for 10 to 19 years of use was 80% higher risk than non-users, and increased to a 220% higher risk than non-users for women who took estrogen for 20 or more years.