Menopausal hormone therapy and risk of ovarian cancer in the European prospective investigation into cancer and nutrition

The association between menopausal hormone therapy (HT) and risk of ovarian cancer was assessed among 126,920 post-menopausal women recruited into the European Prospective Investigation into Cancer and Nutrition. After an average of 9-year follow-up, 424 incident ovarian cancers were diagnosed. Cox models adjusted for body mass index, smoking status, unilateral ovariectomy, simple hysterectomy, age at menarche, number of full-term pregnancies, and duration of oral contraceptives were used. Compared with baseline never use, current use of any HT was positively associated with risk (HR [hazard ratio], 1.29; 95% CI [confidence interval], 1.01-1.65), while former use was not (HR, 0.96; 9 % CI, 0.70-1.30). Current estrogen-only HT was associated with a 63% higher risk (HR, 1.63; 95% CI, 1.08-2.47), while current estrogen plus progestin was associated with a smaller and non-significant higher risk (HR, 1.20; 95% CI, 0.89-1.62). Use of tibolone was associated with a twofold greater risk (HR, 2.19; 95% CI, 1.06-4.50), but was based on small numbers. In conclusion, women who currently use HT have a moderate increased risk of ovarian cancer, and which may be stronger for estrogen-only than estrogen plus progestin preparations.