RATIONALE: Estrogen can cause the growth of breast cancer cells. Hormone therapy, using tamoxifen citrate, may fight breast cancer by blocking the use of estrogen by the tumor cells. Aromatase inhibitors, such as anastrozole, letrozole, and exemestane, may fight breast cancer by lowering the amount of estrogen the body makes. Drugs used in chemotherapy work in different ways to stop the growth of tumor cells, either by killing the cells or by stopping them from dividing. It is not yet known whether giving tamoxifen citrate, anastrozole, letrozole, or exemestane is more effective with combination chemotherapy in treating patients with breast cancer.
PURPOSE: This phase III clinical trial is studying how well giving tamoxifen citrate, anastrozole, letrozole, or exemestane with or without chemotherapy works in treating patients with invasive breast cancer.