Utilization Trend and Comparison of Different Radiotherapy Modes for Patients with Early-Stage High-Intermediate-Risk Endometrial Cancer: A Real-World, Multi-Institutional Study

SIMPLE SUMMARY: The adjuvant treatment for early-stage endometrial cancer (EC) has remained an intractable problem in clinical practice. Although several risk classification strategies have been proposed to guide precise treatment, a significant proportion of patients are still overtreated, especially patients with high-intermediate-risk (HIR) early-stage EC. Here, we compared the survival outcomes between different adjuvant radiotherapy modes in patients with HIR EC defined by three primarily-used criteria, based on multicenter data, to provide further evidence for the adjuvant treatment choices for HIR patients. This study revealed multicentric utilization trends for different radiotherapy (RT) modes for the first time. It confirmed that pelvic external beam radiation therapy (EBRT) showed a survival advantage over vaginal brachytherapy (VBT) alone only in selected patients with HIR. ABSTRACT: This study aimed to compare the outcomes of RT modalities among patients who met different HIR criteria based on multicentric real-world data over 15 years. The enrolled patients, who were diagnosed with FIGO I-II EC from 13 medical institutes and treated with hysterectomy and RT, were reclassified into HIR groups according to the criteria of GOG-249, PORTEC-2, and ESTRO-ESMO-ESGO, respectively. The trends in RT modes utilization were reviewed using the Man-Kendall test. The rate of VBT alone increased from zero in 2005 to 50% in 2015, which showed a significant upward trend (p < 0.05), while the rate of EBRT + VBT utilization declined from 87.5% to around 25% from 2005 to 2015 (p > 0.05). There were no significant differences in OS, DFS, LRFS, and DMFS between VBT alone and EBRT ± VBT in three HIR cohorts. Subgroup analyses in the GOG-249 HIR cohort showed that EBRT ± VBT had higher 5-year DFS, DMFS, and LRFS than VBT alone for patients without lymph node dissection (p < 0.05). Thus, VBT could be regarded as a standard adjuvant radiation modality for HIR patients. EBRT should be administrated to selected HIR patients who meet the GOG-249 criteria and did not undergo lymph node dissection.