This randomized phase II/III trial studies docetaxel, antiandrogen therapy, and radiation therapy to see how well it works compared with antiandrogen therapy and radiation therapy alone in treating patients with prostate cancer that has been removed by surgery. Androgen can cause the growth of prostate cells. Antihormone therapy may lessen the amount of androgen made by the body. Radiation therapy uses high energy x-rays to kill tumor cells and shrink tumors. Drugs used in chemotherapy, such as docetaxel, work in different ways to stop the growth of tumor cells, either by killing the cells, by stopping them from dividing, or by stopping them from spreading. Giving antiandrogen therapy and radiation therapy with or without docetaxel after surgery may kill any remaining tumor cells.