An Open-Label, Randomized, MultiCenter Study to Evaluate the Use of Zolendronic Acid in the Prevention of Cancer Treatment-Related Bone Loss in Postmenopausal Women With Estrogen Positive and/or Progesterone Positive Breast Cancer Receiving Letrozole as Adjuvant Therapy

Post-menopausal breast cancer patients will receive letrozole 2.5 mg daily for the treatment of breast cancer and will be randomized to a treatment group to receive either upfront zoledronic acid 4 mg IV 15-minute infusion every 6 months or delayed start zoledronic acid 4 mg IV 15-minute infusion every 6 months. Delayed start zoledronic acid will be initiated when either the Bone Mineral Density T-score is below -2 Standard Deviations at either the lumbar spine or hip or any clinical fracture unrelated to trauma or an asymptomatic fracture discovered at the month 36 scheduled visit. Letrozole 2.5 mg will be given daily for 5 years.