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

RATIONALE: Diagnostic procedures, such as bone mineral density testing and x-ray, help measure bone loss in women receiving treatment for breast cancer. The test results may help doctors plan better treatment.

PURPOSE: This phase III trial is studying 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.

Eligibility Criteria:
DISEASE CHARACTERISTICS:

* Diagnosis of breast cancer

  * Resected disease
* Enrolled on protocol IBCSG-1-98

  * Receiving adjuvant endocrine therapy comprising 1 of the following regimens:

    * Letrozole
    * Tamoxifen
    * Letrozole after 2 years of tamoxifen
    * Tamoxifen after 2 years of letrozole
  * Not yet completed 5 years of treatment
* No breast cancer recurrence or second primary cancer
* No known, symptomatic bone disease, including osteomalacia or osteogenesis imperfecta
* No prior registration to protocol IBCSG-1-98 Bone Mineral Density substudy
* Hormone receptor status:

  * Estrogen receptor-positive 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
* No patients for whom the bone density determination is impossible

PRIOR CONCURRENT THERAPY:

* See Disease Characteristics
* More than 1 year since prior and no concurrent anticonvulsants
* More than 6 weeks since prior and no concurrent corticosteroids (at doses \> the equivalent of 5 mg/day 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 prior treatment, either investigational or not, for the prevention of osteoporosis (excluding calcium or cholecalciferol \[vitamin D\])
* No concurrent raloxifene
* Concurrent therapeutic intervention for osteoporosis comprising bisphosphonates allowed
* Concurrent warfarin allowed provided it is given for ≤ 4 weeks