Inclusion Criteria

DISEASE CHARACTERISTICS:

- Enrolled on protocol IBCSG-1-98

- Currently receiving (i.e., have not yet completed) 5 years of treatment with
tamoxifen or letrozole and expected to receive ≥ 6 months of additional
treatment on protocol IBCSG-1-98

- No recurrent breast cancer or second primary cancer

- No known bone disease (including osteomalacia or osteogenesis imperfecta)

- Hormone receptor status

- Estrogen and/or progesterone receptor positive tumor

PATIENT CHARACTERISTICS:

- Female

- Postmenopausal

- No uncontrolled thyroid or parathyroid disease, Cushing's disease, or other pituitary
diseases

- No malabsorption syndrome or clinically relevant vitamin D deficiency

PRIOR CONCURRENT THERAPY:

- See Disease Characteristics

- More than 1 year since prior and no concurrent anticonvulsants

- More than 6 months since prior and no concurrent corticosteroids at doses > the
equivalent of 5 mg/day of prednisone for > 2 weeks total

- No prior or concurrent sodium fluoride at daily doses ≥ 5 mg/day for > 1 month

- More than 12 months since prior and no concurrent anabolic steroids

- More than 6 months since any prior drug for the prevention of osteoporosis (excluding
calcium or cholecalciferol [vitamin D])

- Concurrent warfarin allowed provided duration of treatment is no more than 4 weeks