Mifepristone (RU-486) in Androgen Independent Prostate Cancer

Inclusion Criteria: * Histologic documentation of adenocarcinoma of the prostate * Bone metastasis(es) by bone scan or cat scan * Clinical, biochemical, or radiographic progression after primary androgen ablation with either orchiectomy or gonadotropin releasing hormone analog therapy. * One prior chemotherapy treatment is allowed. * \> 3 weeks since major surgery * \> 4 weeks since radiotherapy * \> 8 weeks since prior strontium-89 or samarium 153 * ECOG performance status 0 or 1 * Absolute neutrophil count (ANC) \> 1,500/ul * Platelets \> 100,000/ul * Bilirubin \< 1.5 x upper limit of normal (ULN) * AST or ALT \< 3 x ULN * Creatinine \< 1.5 x ULN * Electrolytes within 10% of normal range * Serum testosterone \< 50ng/dL * Prostate-specific antigen (PSA) \> 5.0ng/ml Exclusion Criteria: * Concomitant therapy with corticosteroids * Chemotherapy within 28 days * Currently active second malignancy other than non-melanoma skin cancer * Baseline adrenal insufficiency requiring long-term steroids