Impact of External Radiotherapy on Survival after Stage I ndometrial Cancer: Results from a Population-Based Study

Purpose: To assess the impact of external radiotherapy on the survival of patients with early stage endometrial cancer in a population-based setting. Patients and methods: Using information from the Geneva Cancer Registry, we identified all patients who underwent operations for endometrial cancer between 1980 and 1996. We excluded patients with tumours that had spread beyond the uterus, patients without myometrial invasion and patients with poorly differentiated, deeply invasive tumours. Adjusting for other prognostic variables, a Cox proportional hazards analysis was used to calculate the diseasespecific risks and the overall mortality risks in patients treated with brachytherapy or external radiotherapy compared with non-irradiated patients. Stratified analyses were performed for patients with 'low-risk' (superficial myometrial invasion, grades 1-2) and 'high-risk' (superficial invasion grade 3 or deep invasion grades 1-2) tumours. Results: For the 162 patients with low-risk tumours, external radiotherapy was significantly associated with an increased overall mortality (hazard ratio [HR]: 6.4, 95% CI: 1.3-30.2) and endometrial cancer mortality (HR: 9.4, 95% CI: 1.0-86.7). In the group of patients with high-risk tumours (n=108), neither brachytherapy nor external radiotherapy modified the endometrial cancer mortality risk. Conclusion: External radiotherapy does not reduce mortality from early stage endometrial cancer and is associated with a significantly increased overall and endometrial cancer mortality risk among patients with superficially invasive grade 1-2 tumours.