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

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.

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])