What is the standard treatment for estrogen receptor-positive breast cancer?

The standard treatment for estrogen receptor-positive breast cancer is tamoxifen. Tamoxifen is a selective estrogen receptor modulator (SERM) that binds to estrogen receptors on breast cancer cells, inhibiting their growth and proliferation. This is particularly effective in estrogen receptor-positive tumors, as these cancers rely on estrogen for their growth. By blocking estrogen from binding to its receptor, tamoxifen reduces the risk of recurrence and can improve overall survival rates in patients with this type of breast cancer.

In contrast, trastuzumab is a monoclonal antibody used primarily for HER2-positive breast cancer, not for estrogen receptor-positive cancer. Immunotherapy has shown promise in various cancer types, but its role in treating early-stage estrogen receptor-positive breast cancer is not standard practice. Rifampin, an antibiotic primarily used to treat tuberculosis, has no role in treating breast cancer.

Thus, tamoxifen remains the cornerstone of hormonal therapy for estrogen receptor-positive breast cancer, making it the appropriate choice in this scenario.