Patients with prostate cancer who are treated with surgery or radiation often develop recurrence of their cancer which is manifest only by a rising PSA (Prostate Specific Antigen) level. Many of these patients are treated with hormone therapy. After a fall in the PSA, these patients eventually display evidence of tumor progression clearly demonstrated by another rise in PSA level while receiving hormone therapy. Evaluation for evidence of tumor spread is usually negative. There is currently no effective therapy approved for use in these patients.