 Bone Mineral Density BMD as measured by X-ray shows the amount of calcium in the bone. Low BMD may reflect osteoporosis, a condition where there is an increased risk of fracture. Women who have gone through menopause have a higher risk of getting osteoporosis because they lose calcium from their bones much faster than younger women. Women with breast cancer may have an additional risk for getting osteoporosis because of the effects of their treatment with chemotherapy. The purpose of this study is to see what levels of BMD post-menopausal women with breast cancer have, and to see if the level of BMD changes during a womens treatment after her surgery. This trial studies changes in BMD and markers of bone activity in women receiving treatment for early stage breast cancer. 