RATIONALE: Drugs used in chemotherapy, such as doxorubicin, epirubicin, and cyclophosphamide, work in different ways to stop the growth of tumor cells, either by killing the cells or by stopping them from dividing. Giving combination chemotherapy after surgery may kill any tumor cells that remain after surgery. Sometimes, after surgery, the tumor may not need more treatment until it progresses. In this case, observation may be sufficient. It is not yet known whether giving doxorubicin or epirubicin together with cyclophosphamide is more effective than observation in treating older women with invasive breast cancer.