This study compares radiation plus chemotherapy with radiation alone in treating women with endometrial cancer that is classified as high risk or advanced stage. Participants will be divided into two groups. Both groups will receive radiation treatment in the pelvic region, while one group will also receive chemotherapy at the same time as radiation, followed by adjuvant chemotherapy. The chemotherapy given at the same time as radiation treatment is called cisplatin and is administered by intravenous drip on days 1 and 22. The adjuvant chemotherapy is a combination of carboplatin and paclitaxel and is administered in 4 cycles at 3 week intervals. For the group receiving radiation and chemotherapy, the treatment extends over 5 months. For the group receiving radiation alone, treatment goes for 6 weeks. All participants are monitored for 10 years. The study aims to see whether combining chemotherapy with radiotherapy treatment, compared with radiotherapy alone, improves overall survival rates, and also looks at quality of life.