This 10-year prospective cohort study, known as the Dayton study, evaluated the incidence of invasive breast cancer (IBC) in 1,267 pre- and postmenopausal women treated with subcutaneous testosterone (T) implants, with or without the aromatase inhibitor anastrozole (T+A), for hormone deficiency symptoms. Over 5,667 person-years of follow-up, 11 cases of
