Prevention of Symptomatic Skeletal Events With Denosumab Administered Every 4 Weeks Versus Every 12 Weeks

Inclusion Criteria: * Patient has given written informed consent. * Histologically confirmed diagnosis of breast or prostate cancer before randomization. * Patient has metastatic breast cancer (stage IV, all subtypes allowed) or prostate cancer (stage IV) and bone metastases and is planned to receive or is receiving antineoplastic treatment. * Patients with prostate cancer must have evidence of disease progression on continuous androgen deprivation therapy (CRPC). * Patients must have ≥ 3 bone metastases (lytic or blastic or mixed). The lesions must be documented by radiological evaluation within 12 weeks before randomization (by X-Ray, CT scan, PET-CT, MRI scan or bone scintigraphy). * WHO performance status 0-2 * Age ≥ 18 years. * Corrected serum calcium ≥ 2 mmol/l and ≤ 3 mmol/l (medical treatments to obtain serum calcium levels in the normal range are allowed, as far as no denosumab is used. Maximally 1 dose of bisphosphonates in the case of hypercalcemia is allowed, if the bisphosphonate was applied at least 3 weeks before the first dose of denosumab). * Liver transaminases not more than 1.5 x ULN or not more than 3 x ULN with liver metastases. Serum total bilirubin ≤ 1.5 x ULN (≤ 2.0 x ULN in case of known Gilbert's disease) * Women are not breastfeeding. Women with child-bearing potential are using effective contraception, are not pregnant and agree not to become pregnant during participation in the trial and during the 12 months thereafter. A negative pregnancy test …