Chemotherapy With or Without Biological Therapy in Treating Patients With Metastatic Prostate Cancer That Has Not Responded to Hormone Therapy

RATIONALE: Drugs used in chemotherapy use different ways to stop tumor cells from dividing so they stop growing or die. Combining more than one drug may kill more tumor cells. Biological therapies use different ways to stimulate the immune system and stop cancer cells from growing. It is not yet known which treatment regimen is more effective in treating metastatic prostate cancer. PURPOSE: Randomized phase II trial to compare the effectiveness of combination chemotherapy with that of chemotherapy plus biological therapy in treating patients who have progressive or metastatic prostate cancer that has not responded to hormone therapy.