 RATIONALE: Drugs used in chemotherapy, such as methotrexate, cyclophosphamide, and liposomal doxorubicin, work in different ways to stop the growth of tumor cells, either by killing the cells or by stopping them from dividing. Giving chemotherapy after surgery may kill any tumor cells that remain after surgery. It is not yet known whether giving liposomal doxorubicin after surgery is more effective than observation or cyclophosphamide and methotrexate in treating breast cancer. 