Breast cancer and HRT--what are the data?

Area of Science:

• Oncology
• Endocrinology
• Epidemiology

Background:

• Breast cancer is a major health concern for women.
• Historically, estrogen was used to treat advanced breast cancer.
• Current research questions if hormone replacement therapy (HRT) increases breast cancer risk.

Purpose of the Study:

• To evaluate the relationship between hormone replacement therapy and breast cancer incidence.
• To synthesize findings from epidemiological studies on HRT and breast cancer risk.
• To assess the clinical significance of HRT's impact on breast cancer.

Main Methods:

• Review of epidemiological studies and clinical trials.
• Analysis of data from large prospective cohorts, including the Nurses' Health Study and Sellers et al. study.
• Examination of the impact of HRT duration and discontinuation on breast cancer risk.

Main Results:

• Some studies suggest a slight increase in breast cancer risk with prolonged HRT use (e.g., relative risk >1.4 in Nurses' Health Study).
• However, the overall evidence indicates a small increase in relative risk with ever-use of HRT.
• Discontinuation of HRT for 2-5 years appears to eliminate the increased risk.
• A prospective cohort study found HRT not associated with significantly increased breast cancer incidence but with reduced total mortality.

Conclusions:

• The collective data suggests that substantial clinical risk of breast cancer associated with HRT use is difficult to ascertain.
• Ongoing trials, such as the Women's Health Initiative, will further clarify any appreciable risks.
• HRT may be associated with reduced overall mortality despite concerns about breast cancer risk.