Links between hormone replacement therapy and neoplasia

Area of Science:

• Reproductive Endocrinology
• Oncology
• Epidemiology

Background:

• Exogenous estrogens and progestins are widely used in hormone replacement therapy (HRT) for postmenopausal women.
• Understanding their impact on gynecologic and breast cancer risk is crucial for clinical decision-making.
• Existing literature presents varied findings on these associations.

Purpose of the Study:

• To synthesize and evaluate the existing epidemiologic literature.
• To assess the relationship between exogenous estrogens and progestins and the risk of breast and endometrial cancers.
• To identify specific risk factors and patterns of use associated with these cancers.

Main Methods:

• Comprehensive review of published epidemiologic literature.
• Inclusion of population-based and hospital-based studies.
• Focus on postmenopausal women using sex steroid hormones in HRT regimens.

Main Results:

• Estrogen replacement therapy (ERT) is associated with a nearly 10-fold increase in endometrial cancer risk after 10-15 years, though cancers are typically low-grade with good prognosis.
• Concurrent use of progestin for at least 10 days per month effectively reduces or eliminates the estrogen-induced endometrial cancer risk.
• Long-term ERT is linked to a modest increase in breast cancer risk (RR ~1.3-1.5), with potential for higher risk when combined with progestins; the effect of continuous low-dose progestin is unknown.

Conclusions:

• Estrogens significantly elevate endometrial cancer risk, but this can be effectively managed with progestin addition.
• While ERT shows a modest increase in breast cancer risk, specific subgroups may be at higher risk.
• Further research is needed on the effects of continuous low-dose progestin combined with estrogen on breast cancer risk.