Isotretinoin, Interferon Alfa-2b, Docetaxel, and Estramustine in Treating Patients With Metastatic Prostate Cancer That Did Not Respond to Hormone Therapy

RATIONALE: Isotretinoin may help prostate cancer cells become more like normal cells, and to grow and spread more slowly. Interferon alfa-2b may interfere with the growth of tumor cells. Drugs used in chemotherapy, such as docetaxel and estramustine, work in different ways to stop the growth of tumor cells, either by killing the cells or by stopping them from dividing. Giving isotretinoin and interferon alfa-2b together with docetaxel and estramustine may kill more tumor cells. PURPOSE: This phase II trial is studying how well giving isotretinoin and interferon alfa-2b together with docetaxel and estramustine works in treating patients with metastatic prostate cancer that did not respond to hormone therapy.