Comparing Continuation or De-escalation of Bone Modifying Agents (BMA) in Patients Treated for Over 2 Years for Bone Metastases From Either Breast or Castration-resistant Prostate Cancer

Inclusion Criteria: * Patients with either radiologically and/or histologically confirmed bone metastases from castrate resistant prostate cancer or breast cancer who are currently receiving BMA * Patient has received BMA for 2 or more years counting from the first BMA dose for bone metastases * Age 18 years or older * Able to provide verbal consent Exclusion Criteria: * Definite contraindication for BMA * History of, or current evidence of osteonecrosis of the jaw * Radiotherapy or surgery to the bone planned within 4 weeks after randomization * Current hypercalcemia defined as corrected serum calcium of \> 3 mmol/L (from standard bloodwork completed within one month prior to treatment dose)