 - Presence of metastatic prostate cancer that fulfills at least one evaluation category as listed: Measurable Disease: Lesions that can be accurately measured in at least one dimension with the longest diameter 20 mm using conventional techniques or 10 mm with spiral CT scan or otherwise at least twice the reconstruction interval for CT or MRI scans. Non-measurable disease: Lesions noted on imaging studies including metastatic bone lesions on bone scan or other non-measurable lesions as defined by the modified RECIST criteria. Progressive disease following a cytotoxic chemotherapy regimen for prostate cancer. 