 RATIONALE: Chemoprevention is the use of certain drugs to keep cancer from forming, growing, or coming back. Estrogen can cause the growth of breast cancer cells. Hormone therapy using letrozole may prevent breast cancer by lowering the amount of estrogen the body makes. Zoledronate may prevent bone loss caused by letrozole. Giving letrozole together with zoledronate may prevent breast cancer and reduce bone loss. 