ETHAN - ET for Male BC

This is an open-label, multicenter, randomized trial for men with stage I-III hormone receptor-positive (HR+)/HER2-negative breast cancer. The trial will have two phases: A 3-week window phase containing endocrine therapy followed by a 4-month treatment phase where participants are treated with one of four endocrine therapy treatment combinations. Tamoxifen is the standard of care for the treatment of breast cancer in men. Anastrozole is a standard treatment in women with breast cancer and works more effectively than tamoxifen. This study hopes to learn if anastrozole may also be effective in men. Given that gonadal suppression and CDK 4/6 inhibitors have both improved treatment in women with breast cancer, the study hopes to learn how the addition of Degarelix (gonadal suppression) and Abemaciclib (CDK 4/6 inhibitors) work in comparison to standard of care tamoxifen. The research study procedures include screening for eligibility and study treatment including laboratory evaluations and quality of life questionnaires. After completion of treatment, participants will be followed for up to 10 years It is expected that about 60 men will take part in this research study. Eli Lilly, a pharmaceutical company, is supporting this research study by providing one of the study drugs. This study is also being supported by Johns Hopkins University on behalf of the Translational Breast Cancer Research Consortium (TBCRC).