An abbreviation for a chemotherapy combination used with other types of therapy to treat breast cancer, including breast cancer that has spread or come back. It includes the drugs doxorubicin hydrochloride (Adriamycin) and cyclophosphamide. Also called AC. OR A chemotherapy regimen consisting of doxorubicin hydrochloride (Adriamycin) and cyclophosphamide used in the adjuvant setting for the primary treatment of breast cancer. This regimen is also used for the treatment of recurrent and metastatic breast cancer.