Estrogen-alone therapy and invasive breast cancer incidence by dose, formulation, and route of delivery: findings from the WHI observational study

This 2018 analysis from the Women’s Health Initiative Observational Study evaluated the relationship between estrogen-alone hormone therapy and invasive breast cancer incidence among 26,525 postmenopausal women with a hysterectomy. Over an average follow-up of 8.2 years, the study found no significant differences in breast cancer risk when comparing low-dose (