The ODYSSEY TRIAL Phase IV Trial Evaluating the Palliative Benefit of Pamidronate or Zoledronic Acid in Breast Cancer

This study will be a prospective, randomized, double-blind, placebo controlled, Phase IV study of pamidronate vs. zoledronic acid in women with breast cancer and bone metastases. Patients who are at high-risk of subsequent SREs will be screened for entry into this study. High-risk will be defined as fulfilling one or more of the following criteria: elevated sCTX (\>400ng/L) and/or bone pain and/or a prior SRE and/or progression of bone disease (by imaging) despite at least 3 months of pamidronate therapy. Patients who meet the eligibility criteria, will be randomized to receive 3 cycles of intravenous zoledronic acid (4mg intravenously over 15 minutes) or to continue their standard dose of pamidronate. Both treatments will be given at 4 week intervals. Patients will be stratified according to whether or not they have had a SRE prior to study entry, progressive bone disease or bone pain. In order for the study to be double-blind, patients will receive two infusions simultaneously, at each study visit, one of the active drug and another of the placebo. After completing 3 cycles of study treatment, patients will resume their monthly intravenous pamidronate infusions as per current standard of care.