ESTRO 2025 - Abstract Book

S779

Clinical - Gynaecology

ESTRO 2025

1 Department of Radiation Oncology, Washington University School of Medicine, St. Louis, USA. 2 Department of Radiation Oncology, Keck School of Medicine, University of Southern California, Los Angeles, USA. 3 Radiation Oncology, Washington University School of Medicine, St. Louis, USA. 4 Department of Obstetrics and Gynecology, Division of Gynecologic Oncology, Washington University School of Medicine, St. Louis, USA. 5 Department of Statistics, Washington University School of Medicine, St. Louis, USA. 6 Personalized Radiation Oncology, Cancer Care Specialists, Reno, USA Purpose/Objective: Recent data suggest that adjuvant hypofractionated radiotherapy (h-RT) may be appropriate for patients with high intermediate risk endometrial cancer i ; however, in the locally advanced setting, the safety and efficacy of this approach is unknown. We evaluated the safety of h-RT sequenced after chemotherapy for patients with locally advanced endometrial cancer. Material/Methods: Patients with stage III-IVA endometrioid adenocarcinoma or any stage serous, clear cell, or carcinosarcoma of the uterus, were enrolled in this phase I trial (NCT04386993). All patients underwent total hysterectomy, adjuvant chemotherapy, and re-staging CT chest/abdomen/pelvis. Patients were then offered h-RT if no progression precluding radiotherapy was identified. h-RT was intensity-modulated radiation therapy 25 Gy in 5 fractions delivered once daily to the vaginal cuff and pelvic lymph nodes. After 17 patients were enrolled, the protocol was amended to allow for a vaginal cylinder brachytherapy boost (18 Gy in 3 fractions to the surface), per physician preference. The primary outcome of this study was to evaluate acute (0-90 days post-h-RT) and late (90-360 days post-h-RT) high-grade (G3-5) gastrointestinal (GI), genitourinary (GU), and hematologic toxicities using the CTCAE version 5.0. Baseline and treatment characteristics were collected including molecular profiling data as well as disease outcome measures including locoregional control, distant control, disease free survival (DFS), and overall survival (OS). Results: Baseline and treatment characteristics are demonstrated in Table 1. Most patients (21/25) completed 6 cycles of chemotherapy, and all patients (25/25) completed h-RT. The rate of G3-5 acute GI, GU, and hematologic toxicity was 0% (0/25), 0% (0/25), and 12% (3/25), respectively. The rate of G3-5 late GI, GU, and hematologic toxicity was 0% (0/25), 0% (0/25), and 4% (1/25). At a median follow-up of 21.2 months from first chemotherapy treatment and 15.9 months from first radiation treatment, there were no locoregional failures and five distant failures. 1-year locoregional control, distant control, DFS, and OS were 100%, 80%, 80%, and 91%, respectively.