Randomized phase III trial to compare the effectiveness of two combination chemotherapy regimens plus radiation therapy in treating patients who have stage III or stage IV endometrial cancer. Radiation therapy uses high-energy x-rays to damage tumor cells. Drugs used in chemotherapy use different ways to stop tumor cells from dividing so they stop growing or die. Combining more than one chemotherapy drug with radiation therapy may kill more tumor cells. It is not yet known which combination chemotherapy regimen plus radiation therapy is more effective for endometrial cancer.