Study to Evaluate Zoledronic Acid on Quality of Life and Skeletal-related Events as Adjuvant Treatment in Patients With Hormone-naïve Prostate Cancer and Bone Metastasis Who Have Undergone Orchiectomy

Inclusion Criteria: * Age ≥18 * histologically confirmed adenocarcinoma of the prostate. * Orchidectomy within the four previous weeks to enter the study. * bone metastasis evidenced by bone scan. * A hip DEXA study with a DS \< 3. * No hormonal therapy previous to enter the study. * ECOG performance score of 0-2. * Signed written informed consent. Exclusion Criteria: * Abnormal renal function evidenced by a creatinine clearance ≤60 ml/min. * Any kind of hormonal therapy for prostate cancer previous to enter the study. * Serum calcium corrected for albumin level \< 8.0 mg/dl. * WBC \< 3.0x10\^3, ANC \< 1500/mm3, Hemoglobin \< 8.0 g/dl, platelets \< 75 x 10\^3/l. * Abnormal hepatic function evidenced by ALT and AST value \>2.5 UNL * Subjects with any other malignant disease that can affect the bone. * Subjects with any other non malignant disease that can jeopardize the evaluation of the primary objectives of this trial (severe osteoporosis) or that do not aloud perform the trial evaluations. * Known hypersensibility to zoledronic acid or other bisphosphonates. * Subjects that in the investigator's opinion can not cooperate with the protocol. Other protocol inclusion/exclusion criteria may apply.