Study of Bone Mineral Density in Women With Breast Cancer Treated With Triptorelin and Tamoxifen or Exemestane on Protocol IBCSG 25-02

DISEASE CHARACTERISTICS: * Patient must be eligible and enrolled in the TEXT-2 trial prior to enrolling in TEXT-Bone * Serial bone marrow density (BMD) measurements must be taken within the same institution * Hormone receptor positive PATIENT CHARACTERISTICS: * See Disease Characteristics * Premenopausal * No bone fracture in the past 6 months that, in the investigator's judgement, could be related to bone fragility * No clinical or biochemical malabsorption syndrome, known vitamin D deficiency, active hyper- or hypoparathyroidism, or Paget's disease * No uncontrolled thyroid disease, Cushing disease, or other pituitary diseases * No other bone disease (including osteomalacia or osteogenesis imperfecta) PRIOR CONCURRENT THERAPY: * See Disease Characteristics * At least 6 months since prior and no concurrent bisphosphonate therapy (or other bone therapies such as PTH or strontium) * At least 6 months since prior glucocorticoid (\> 5 mg prednisone or equivalent) for \> 1 month * At least 12 months since prior anticonvulsants