Trastuzumab and Docetaxel in Treating Patients Who Have Metastatic Prostate Cancer That Is Refractory to Hormone Therapy

RATIONALE: Monoclonal antibodies such as trastuzumab can locate tumor cells and either kill them or deliver tumor-killing substances to them without harming normal cells. Drugs used in chemotherapy use different ways to stop tumor cells from dividing so they stop growing or die. Combining monoclonal antibody therapy with chemotherapy may kill more tumor cells. PURPOSE: Phase II trial to compare the effectiveness of trastuzumab alone and in combination with docetaxel in treating patients who have metastatic prostate cancer that is refractory to hormone therapy.