OBJECTIVES: The objectives of this retrospective database study were to estimate the treatment costs for bone fractures in older women (aged 65 years and older) who have early breast cancer and to compare those costs with the treatment costs for bone fractures incurred by older women who do not have breast cancer. METHODS: Direct costs for bone fractures in early breast cancer patients were evaluated using the Medicare 5% sample data (1997-1998), including the estimation of "medical treatment costs for bone fracture," "excess treatment costs for bone fracture," and "excess LTC costs for bone fracture." Inpatient costs, medical treatment costs, and LTC admission rates were compared between a cohort of women with early breast cancer and bone fracture and an age-matched cohort of normal women with bone fracture, stratified by age group, status of hospitalization for bone fracture, and type of bone fracture. RESULTS: For older women with early breast cancer, the "direct cost for bone fracture" was estimated to be about $45,579, 57% of which is for treatment costs of the bone fracture (including 32% of inpatient hospital costs and 25% of non-inpatient hospital costs), 24% for other excess treatment costs, and 18% for excess long-term care costs. CONCLUSIONS: This study represents the first research on the costs of bone fracture in older women with early breast cancer. It shows that bone fracture is costly in this group. However, there is no significant difference between the costs of bone fracture in older women with early breast cancer and older women who do not have breast cancer.