This randomized phase II trial studies radiation therapy and cisplatin to see how well they work compared with radiation therapy alone in treating patients with endometrial cancer that has come back. Radiation therapy uses high-energy x-rays and other types of radiation to kill tumor cells. Drugs used in chemotherapy, such as cisplatin, 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. It is not yet known whether giving radiation therapy together with cisplatin is more effective than radiation therapy alone in treating patients with endometrial cancer.