Hormone replacement therapy formulations and risk of epithelial ovarian carcinoma

Hormone replacement therapy (HRT) has been inconsistently linked to ovarian cancer. Estrogen formulations in HRT vary in their effects on estrogen-sensitive target tissues, such as the ovary. The aim of the study is to evaluate the impact of various HRT formulations and their characteristics of use on the risk of epithelial ovarian carcinoma (EOC).

We assessed the association between the use of HRT and the risk of invasive EOC in women participating in a population-based, case-control study conducted in the Delaware Valley from 1994 to 1998. Cases aged 45 or above at diagnosis (n = 484) were compared to community controls (n = 926) frequency matched by age and area of residence. Information on HRT formulation, timing, and duration were obtained by in-person interview by trained interviewers. HRT formulations were classified as opposed (estrogen + progestin) or unopposed (estrogen alone). They were further categorized according to the estrogen component as either conjugated equine estrogen (CEE), the most common formulation, or non-CEE. Multivariate unconditional logistic regression analyses were used to adjust for age at diagnosis, number of live births, use of oral contraceptives, family history of ovarian carcinoma, and history of tubal ligation.

Overall, no association was found between any use of HRT and EOC. Although use of unopposed non-CEE was associated with a significant decrease in risk among hysterectomized women (OR = 0.17, 95% CI = 0.04,0.82), this was not true for women with an intact uterus (OR = 1.14, 95% CI = 0.44,2.98; P for interaction = 0.049). No significant differences in EOC risk were observed for other HRT formulations.

Our results did not suggest any consistent pattern of altered risk for EOC and the overall use of HRT by specific formulations of HRT.