Bone Density and Bone Loss in Postmenopausal Women With Breast Cancer Receiving Treatment in Clinical Trial IBCSG-1-98

OBJECTIVES: * Compare the effects on bone mineral density (BMD) in the L2-L4 (posterio-anterior) region of the spine and hip by assessing bone density in postmenopausal women with breast cancer receiving treatment on protocol IBCSG-1-98. * Compare the incidence of radiological gross changes and fractures identified from spine x-rays (T4-L4) in these patients (in groups 1 and 2). * Use longitudinal BMD measurements to estimate a linear rate of bone loss based on mixed effect models. * Identify serum markers for bone loss to determine how they correlate with osteoporosis, microfractures, clinical fractures, and breast cancer-related bone events. OUTLINE: This is a multicenter study and a substudy of protocol IBCSG-1-98. Patients are assigned to 1 of 3 groups according to the length of treatment they have undergone on protocol IBCSG-1-98. * Group 1 (prior to or at the end of the second year of treatment on protocol IBCSG-1-98): Patients undergo bone mineral density (BMD) testing of the L2-L4 spine and hip at baseline and years 1, 2, 3, and 4 from baseline. They also undergo x-rays of the T4-L4 spine at baseline and years 1, 3, and 4 from baseline. * Group 2 (after 2 years but before the end of the third year of treatment on protocol IBCSG-1-98): Patients undergo BMD testing of the L2-L4 spine and hip at baseline and years 1, 2, and 3 from baseline. They also undergo x-rays of the T4-L4 spine at baseline and years 2 and 3 from baseline. * Group 3 (after 3 years but before the end of the fifth year of treatment on protocol IBCSG-1-98): Patients undergo BMD testing of the L2-L4 spine and hip at baseline and years 1 and 2 from baseline (for patients in 4th year of treatment) or year 1 from baseline (for patients in 5th year of treatment). Patients undergo blood collection at baseline and periodically during study for biomarker correlative study. PROJECTED ACCRUAL: A total of 660 patients will be accrued for this study.