Objectives: In a prospective study during the years 1986 to 1988, the Danish Endometrial Cancer Group (DEMCA) demonstrated that postoperative radiotherapy was unnecessary for low-risk patients with stage I disease. In the present study, we evaluated in a population-based study if radiotherapy could also be omitted for intermediate-risk patients with stage I disease without loss of survival.

Study Design: From 1998 to 1999, 1166 patients newly diagnosed with carcinoma of the uterus were included in this prospective nationwide study. Of these, 232 were intermediate-risk patients with stage I disease. All intermediate-risk patients received standard primary surgery (hysterectomy, bilateral salpingo-oophorectomy, and peritoneal washings), and no postoperative radiotherapy was given. Survival analyses were performed using Kaplan-Meier survival estimates. The results were compared to the 1986-1988 DEMCA data.

Results: The 5-year overall survival (OS) rate for the entire population was 77% (stages I-IV). The patients with stage I disease were divided into low-, intermediate-, and high-risk; the OS rates were 91%, 78%, and 62%, and the endometrial cancer-specific survival rates were 97%, 87%, and 72%, respectively. Using patients' age, tumor grade, myometrial invasion, we divided the intermediate-risk group into "high risk" intermediate and "low-risk" intermediate with OS rates of 70% and 90% and cancer-specific survival of 81% and 96%, respectively. The OS rate (78%) of the intermediate-risk group after radiation had been omitted was comparable to the OS rate (79%) of the intermediate-risk group in the earlier DEMCA (1986-1988) study where postoperative radiation was still the standard of care.

Conclusion: We conclude that in a population-based study, radiotherapy can be omitted for intermediate-risk patients with stage I endometrial cancer without loss of survival.