Histopathological risk stratification for early-stage endometrial cancer patients receiving adjuvant vaginal brachytherapy.

PURPOSE: This study aims to figure out prognostic factors affecting treatment outcomes for early-stage endometrial cancer patients undergoing adjuvant vaginal brachytherapy (VBT) and to develop a histopathological risk stratification model. MATERIALS AND METHODS: We retrospectively reviewed International Federation of Gynecology and Obstetrics stage I endometrioid endometrial cancer patients who underwent primary surgery followed by VBT from January 2010 to December 2022. The high dose rate VBT was prescribed in either 30 Gy in 6 fractions or 21 Gy in 3 fractions. In order to identify significant factors influencing locoregional recurrence-free survival (LRRFS), disease-free survival (DFS), and overall survival (OS). Patients were stratified into risk groups according to the identified prognostic factors. RESULTS: A total of 217 patients were reviewed with a median follow-up of 58.4 months. The recurrences were observed in 21 cases (9.7%). Distant metastasis accounted for most of the failure pattern (18/21 patients, 85.7%). The 5-year LRRFS, DFS, and OS rates were 94.5%, 91.2%, and 98.7%, respectively. Multivariate analysis revealed three statistically significant prognostic factors for DFS: high grade (hazard ratio [HR], 6.12; p = 0.010), tumor size ≥4 cm (HR, 6.48; p = 0.001), and depth of myometrial invasion ≥50% (HR, 4.97; p = 0.027). Risk stratification based on these factors demonstrated significant differences in DFS only between intermediate and high-risk groups (p = 0.002). CONCLUSION: Our histopathological risk stratification model could successfully differentiate the high-risk group from others in early-stage endometrial cancer patients. This model provides crucial prognostic information and could be helpful, especially in resource-limited settings where molecular classification might not be readily available.