Breast Cancer Incidence and Mortality in Relation to Hormone Replacement Therapy Use Among Postmenopausal Women: Results From a Prospective Cohort Study

Hormone replacement therapy increases the risk of breast cancer, but little evidence assesses the effects of potential interactions of different hormone replacement therapy types on breast cancer. To examine this issue, a total of 689 breast cancer cases and 81 breast cancer deaths were identified during 372,210 person-years of follow-up. The total current hormone replacement therapy use was associated with an increased risk of breast cancer especially for slim women. This study suggests that hormone replacement therapy use was associated with an altered risk of the occurrence of breast cancer in the US postmenopausal women. Hormone replacement therapy (HRT) is associated with increased risk of breast cancer (BC), but little evidence assesses the effects of potential effect-modifiers on HRT-related BC. We sought to examine the relationship of different HRT types/method use and risk of BC in US postmenopausal women. In total, 689 BC cases and 81 BC deaths were identified during 372,210 person-years of follow-up. Cox regression and competing risk regression were used to estimate multivariable-adjusted hazards ratios (HRs) and 95% confidence intervals (95% CIs) by HRT status (never, former, current) for risk of BC incidence and mortality. The total current HRT use was associated with an increased risk of BC (HR current vs. never, 1.67; 95% CI, 1.33, 2.11), but did not associate with risk of death from BC (HR current vs. never, 0.85; 95% CI, 0.40, 1.78). Furthermore, underweight women (BMI <20 kg/m(2), HR current vs. never, 12.05, 95% CI, 1.46, 99.75) were more likely to take increased risk of BC from HRT use compared to the obese (BMI >30 kg/m(2), HR current vs never, 1.19; 95% CI, 0.73, 1.97). This study suggests that HRT use was associated with an altered risk of the occurrence of BC in the US postmenopausal women, especially for underweight women. (C) 2021 Published by Elsevier Inc.

Automated summary

Hormone replacement therapy is associated with increased risk of breast cancer, especially for slim postmenopausal women.