Internal medicine

Systemic therapy

Cancer

Oncology

Estrogen

Antiestrogen

Breast cancer

Cancer research

Medicine

Estrogen receptor

Progesterone receptor

New England Journal of Medicine

ER-positive, HER2-negative breast cancer, which accounts for about 70% of all breast cancers, is heterogeneous. Antiestrogen therapy is the cornerstone of systemic therapy, and its efficacy depends on such factors as grade, Ki-67 labeling, and progesterone receptor expression.

Systemic Therapy for Estrogen Receptor–Positive, HER2-Negative Breast Cancer