Effect of Radiotherapy in Addition to Surgery in Early Stage Endometrial Cancer: A Population-Based Study

SIMPLE SUMMARY: Endometrial cancer is a relatively common tumor among women above the age of 50. The treatment of endometrial cancer in an early stage (FIGO I) is still under dispute. The standard treatment of surgery also includes radiotherapy in certain risk groups. In our study, we assessed the value of radiotherapy (external beam or brachytherapy) on survival in a large population-based cohort of early endometrial cancer cases (FIGO I), with operative treatment respecting known risk factors. The data are based on the epidemiological cancer registries (Robert Koch Institute) from 2000–2017 and encompassed 12,718 cases. We found that radiotherapy is especially beneficial when the tumor infiltrates the muscular tissue (myometrium) of the uterus to a large extend. Radiotherapy was also advantageous in all histopathological grades (cell differentiation). Future studies need to compare different treatment options in an experimental prospective design. ABSTRACT: Background: The role of radiotherapy in the management of early (FIGO I) endometrial cancer is controversial with limited availability of prospective data from randomized trials. Methods: German Epidemiologic Cancer Registries provided by the Robert Koch Institute. We considered FIGO I cases with recorded operative treatment (n = 12,718, 2000–2017). We computed hazard ratios (HR) from relative survival models in relation to the mortality of the general population with 95% confidence intervals (CI). Multivariate models were adjusted for age, stage (IA vs. IB), grading, and chemotherapy. Radiotherapy included external radiotherapy and brachytherapy. Results: Cases with a favorable risk profile (FIGO IA, G1/G2) had a slightly lower survival rate, relative to the general population (FIGO IA: 0.9, G1: 0.91). The proportion of FIGO IA cases was lower in the radiotherapy group (52.6%) vs. cases without radiotherapy (78.6%). Additional treatment with radiotherapy was beneficial in FIGO IB (HR = 0.74) and all histopathological grades, but not FIGO IA cases (HR = 0.93) cases. Compared to IA tumors, IB cases had a HR of 1.51 (95% CI: 1.34–1.7). Conclusions: Radiotherapy in addition to surgery is beneficial for patients in a FIGO IB stage. Further studies need to address the impact of new techniques and risk assessment.