Bone Mineral Density in Postmenopausal Women With Primary Breast Cancer Who Are Receiving Treatment on Clinical Trial CAN-NCIC-MA27

• Percentage change in BMD at 5 years (from baseline) [ Time Frame: 5 years ] [ Designated as safety issue: No ]
• Mean percentage change in BMD at 1, 3, and 5 years (from baseline) [ Time Frame: 5 years ] [ Designated as safety issue: No ]
• Proportion of patients without osteopenia or osteoporosis (stratum I) who develop BMD below the absolute threshold for osteopenia (< -2.0 standard deviation below the mean), suffer any osteoporotic fracture, or have an asymptomatic fracture revealed ... [ Time Frame: 5 years ] [ Designated as safety issue: No ]
• Percentage of patients with osteopenia or osteoporosis (stratum II) who have ≥ 5% improvement of BMD at 2 years post randomization on protocol CAN-NCIC-MA27 and who have clinically apparent osteoporosis-related fracture of the long bones [ Time Frame: 5 years ] [ Designated as safety issue: No ]
• Pattern of change in bone biomarkers from baseline [ Time Frame: 5 years ] [ Designated as safety issue: No ]
• Clinical safety and tolerability of study medications [ Time Frame: 5 years ] [ Designated as safety issue: Yes ]

RATIONALE: Learning about the effect of exemestane and anastrozole on bone mineral density in postmenopausal women with primary breast cancer may help plan treatment, decrease the risk of broken bones, and help patients live more comfortably.

PURPOSE: This phase III trial is studying bone mineral density in postmenopausal women with primary breast cancer who are receiving treatment on clinical trial CAN-NCIC-MA27.

OBJECTIVES:

• Determine whether there is a clinically relevant difference in bone mineral density (BMD) at 2 years in postmenopausal women with primary breast cancer (with or without osteopenia or osteoporosis) treated with exemestane vs anastrozole on protocol CAN-NCIC-MA27.

OUTLINE: This is a multicenter, companion study. Patients are stratified according to baseline bone mineral density (BMD) measurement (T-score* ≥ -2.0 standard deviation [SD] [no osteopenia or osteoporosis] vs T-score* < -2.0 SD).

NOTE: *The lowest of the two T-scores: L1-L4 or total hip

Blood samples for the identification of bone biomarkers (formation marker: serum amino-terminal procollagen 1 extension peptide [P1NP] and resorption marker: serum N-telopeptide) are obtained at baseline and at 6 and 12 months. BMD is determined by dual-energy x-ray absorptiometry (DEXA) at baseline and then annually for 5 years (or for as long as patient is receiving treatment on protocol CAN-NCIC-MA27).

Patients receive oral calcium and oral cholecalciferol (vitamin D) daily. Patients with osteopenia or osteoporosis (stratum II) also receive oral bisphosphonate therapy

PROJECTED ACCRUAL: A total of 408 patients will be accrued for this study.

• Breast Cancer
• Osteoporosis

• Dietary Supplement: calcium carbonate
• Dietary Supplement: calcium citrate
• Dietary Supplement: cholecalciferol
• Drug: alendronate sodium
• Drug: calcium gluconate
• Drug: risedronate sodium
• Other: laboratory biomarker analysis
• Procedure: dual x-ray absorptometry

DISEASE CHARACTERISTICS:

• Enrolled in and meets eligibility requirements for protocol CAN-NCIC-MA27
• Acceptable quality dual-energy x-ray absorptiometry (DEXA) of the L1-L4 postero-anterior spine and hip within 12 weeks prior to randomization on protocol CAN-NCIC-MA27

• Hormone receptor status:

  • Estrogen receptor- and/or progesterone receptor-positive tumor

PATIENT CHARACTERISTICS:

• Female
• Postmenopausal
• No malabsorption syndrome
• No known cholecalciferol (vitamin D) deficiency, active hyper- or hypoparathyroidism, or Paget's disease
• No uncontrolled thyroid disease, Cushing's disease, or other pituitary disease
• No other bone disease (including osteomalacia or osteogenesis imperfecta)

PRIOR CONCURRENT THERAPY:

• More than 6 months since prior drugs (investigational or not), including bisphosphonates, for the prevention of osteoporosis (stratum I)
• More than 12 months since prior and no concurrent anticonvulsants
• More than 6 months since prior and no concurrent corticosteroids at doses > 5 mg/day of prednisone (or equivalent) for > 2 weeks
• More than 12 months since prior and no concurrent anabolic steroids
• No prior bisphosphonates (stratum II)
• No concurrent sodium fluoride at daily doses ≥ 5 mg/day
• No long-term (i.e., > 6 months) use of coumarins
• No concurrent drugs (investigational or not), including bisphosphonates, for the prevention of osteoporosis (for patients with no osteopenia or osteoporosis [stratum I])

• National Cancer Institute (NCI)
• North Central Cancer Treatment Group
• Southwest Oncology Group