This randomized phase III trial studies carboplatin and paclitaxel to see how well they work with or without cisplatin and radiation therapy in treating patients with stage I-IVA endometrial cancer. Drugs used in chemotherapy, such as carboplatin, paclitaxel, and 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. Radiation therapy uses high-energy x-rays to kill tumor cells. Giving chemotherapy and radiation therapy after surgery may kill any tumor cells that remain after surgery. It is not yet known whether carboplatin and paclitaxel are more effective with or without cisplatin and radiation therapy in treating patients with endometrial cancer.