Online Program

WITHDRAWN: Adjuvant endocrine therapy for breast cancer and a natural experiment

Joan Neuner, Medical College of Wisconsin 
Elizabeth C Smith, Medical College of Wisconsin 
Rodney Allen Sparapani, Medical College of Wisconsin 

Keywords: aromatase inhibitors, causal inference, instrumental variables, local average treatment effect

Post-menopausal breast cancer survivors whose tumor is estrogen or progesterone receptor positive will typically be prescribed adjuvant endocrine therapy to prevent a recurrence of their breast cancer. Endocrine therapy mainly falls into two drug classes: Selective Estrogen Receptor Modulators (SERMs) and Aromatase Inhibitors (AIs). SERMs were the first generation therapy; currently, the SERM Tamoxifen, which is generic, is less popular than second generation AIs such as Anastrozole which only recently went generic in July 2010. We intend to study the natural experiment created when the generic Anastrozole became a cheaper competitor to the brand name drug already on the market. Drug economics can be an important consideration in the adherence and persistence of drug therapy which has serious implications for health care outcomes and policy.