OBJECTIVES: I. Compare the percentage one year survival rate in hormone refractory prostate cancer patients treated with leflunomide (SU101), mitoxantrone, and prednisone versus mitoxantrone and prednisone alone. II. Compare the palliative pain response, time to treatment failure, time to progression, median survival, investigator global response assessment, objective response, time to palliative pain response, duration of palliation, and effect on PSA between these two regimens. III. Assess the safety and tolerability of mitoxantrone in combination with SU101 in these patients. IV. Assess the health related quality of life of these patients on these regimens.