Hormone replacement therapy and breast cancer

Area of Science:

• Endocrinology
• Oncology
• Women's Health

Background:

• Numerous studies on estrogen replacement therapy (ERT) have not linked exogenous estrogen to increased breast cancer risk in post-menopausal women.
• The relative risk (RR) for breast cancer in estrogen users typically hovers around 1.0, indicating no significant increase.
• Emerging evidence suggests progesterone deficiency might elevate breast cancer risk in certain women.

Purpose of the Study:

• To evaluate the impact of estrogen and progestogen in hormone replacement therapy (HRT) on breast cancer risk.
• To clarify the role of progestogens in mitigating potential breast cancer risks associated with HRT.

Main Methods:

• Review of epidemiological and clinical reports on hormone use and breast carcinoma.
• Analysis of relative risk (RR) data comparing estrogen users, unopposed estrogen users, and estrogen-progestogen users.

Main Results:

• The RR for breast cancer in estrogen users generally ranges from 0.4 to 3.4, with most studies reporting an RR close to 1.0.
• Studies indicate that adding progestogen to ERT may significantly decrease breast cancer risk, with RRs ranging from 0.47 to 0.89 when compared to unopposed estrogen.
• Estrogen therapy alone does not appear to increase breast cancer risk.

Conclusions:

• Combination estrogen-progestogen therapy is recommended for HRT, even in women without a uterus.
• This combination therapy may offer a reduced risk of breast cancer for some women.
• Progestogens are not primarily added to counteract estrogen-induced breast cancer risk, as such a risk is not established.