ESTRO 2025 - Abstract Book

S807

Clinical - Gynaecology

ESTRO 2025

1306

Mini-Oral The impact of positive peritoneal cytology on FIGO 2023 stage IC endometrial cancer outcomes Alper Kahvecioglu 1 , Sezin Yuce Sari 1 , Melis Gultekin 1 , Ecem Yigit 1 , Zafer Arik 2 , Alp Usubutun 3 , Nejat Ozgul 4 , Ferah Yildiz 1 1 Radiation Oncology, Hacettepe University Faculty of Medicine, Ankara, Turkey. 2 Medical Oncology, Hacettepe University Faculty of Medicine, Ankara, Turkey. 3 Pathology, Hacettepe University Faculty of Medicine, Ankara, Turkey. 4 Gynecology, Hacettepe University Faculty of Medicine, Ankara, Turkey Purpose/Objective: FIGO 2023 stage IC endometrial cancer is a rare subtype defined by aggressive histology without myometrial invasion. This study evaluated the clinical outcomes of patients with FIGO stage IC endometrial cancer treated with adjuvant radiotherapy (RT). Material/Methods: We retrospectively reviewed the medical records of 1,297 patients with endometrial cancer who underwent adjuvant RT following surgical staging. A total of 28 patients with FIGO stage IC disease were included. Results: The majority of patients had serous carcinoma (39%), followed by clear cell carcinoma (25%) and high-grade endometrioid carcinoma (25%). Half of the patients received RT alone, while the other half received combined RT and chemotherapy. The most common RT technique was vaginal brachytherapy (VBT), used in 86% of cases. The median VBT dose was 27.5 Gy (range: 21–28 Gy) in 3–5 fractions, while the median dose of external beam radiotherapy (EBRT) was 50.4 Gy (range: 45–50.4 Gy) in 25–28 fractions. The median follow-up duration was 59 months. During this period, recurrence was observed in 7 (25%) patients, with a local recurrence rate of 7% and a distant metastasis (DM) rate of 21%. The 2- and 5-year overall survival (OS) rates were 96% and 87%, respectively. Locoregional recurrence-free survival (LRRFS) rates were 96% and 82%, and distant metastasis-free survival (DMFS) rates were 92% and 80%. Positive peritoneal cytology was associated with significantly lower 5-year OS (93% vs. 33%, p < 0.05), LRRFS (86% vs. 33%, p < 0.05), and DMFS (90% vs. 0%, p < 0.05) compared to patients with negative peritoneal cytology (Figure 1). The addition of chemotherapy did not improve outcomes. No severe treatment-related toxicity was observed. Figure 1. Kaplan-Meier survival curves showing survival rates stratified by peritoneal cytology.

Conclusion: Patients with FIGO 2023 stage IC endometrial cancer have a favorable prognosis, except when positive peritoneal cytology is present. In patients with positive peritoneal cytology, a more intensive treatment such as adding chemotherapy should be considered.

Keywords: Endometrial cancer, FIGO 2023, radiotherapy