ESTRO 2025 - Abstract Book

S794

Clinical - Gynaecology

ESTRO 2025

and iliac crest planes was 0.68 cm (IQR -8.13 ─ 5.72) and -1.16 cm (IQR -10.57 ─ 7.60), respectively. The median distance from the ovary edge to the PTV was 1.83 cm (IQR -0.49 ─ 5.99). The median maximum and mean ovarian doses were 25.1 Gy (IQR 7.3 ─ 53.7) and 14.3 Gy (IQR 4.5 ─ 52.8), respectively. The median V5.5 Gy and V7.5 Gy were 100% (IQR 26.7 ─ 100% and 0 ─ 100%, respectively). Six (40%) patients had ovary-sparing RT plans. Ovarian location outside PTV was significantly inversely correlated with ovarian maximum (-0.86, p<0.0001) and mean (-0.7, p<0.0001) doses. At a median follow-up of 20 months, 12 patients (80%) had menopausal symptoms. Endocrine function was assessed in 6 patients, all of whom had premature ovarian insufficiency (POI). Conclusion: Positioning the ovaries outside the PTV significantly reduces radiation dose. Although most ovaries were outside the PTV, the majority received RT doses associated with POI, highlighting the challenges of achieving optimal ovarian sparing. We emphasize the importance of early multidisciplinary discussion to optimize surgical planning and to predict the clinical benefit of OT. References: 1. Gay C, Raphael YR, Steers J, et al. Ovarian Transposition Before Pelvic Radiation Therapy: Spatial Distribution and Dose Volume Analysis. Adv Radiat Oncol . 2022;7(1). doi:10.1016/j.adro.2021.100804 2. Lv XJ, Cheng XL, Tu YQ, Yan DD, Tang Q. Association between the location of transposed ovary and ovarian dose in patients with cervical cancer treated with postoperative pelvic radiotherapy. Radiation Oncology . 2019;14(1). doi:10.1186/s13014-019-1437-3 3. Yin L, Lu S, Zhu J, Zhang W, Ke G. Ovarian transposition before radiotherapy in cervical cancer patients: Functional outcome and the adequate dose constraint. Radiation Oncology . 2019;14(1). doi:10.1186/s13014-019-1312-2 Digital Poster Adjuvant Chemotherapy Versus Chemotherapy and Radiation Therapy in Patients With Stage III Endometrial Cancer: A Propensity Score Matching Study Khemanat Khemworapong 1 , Janjira Petsuksiri 2 , Atthapon Jaishuen 1 , Jiraporn Setakornnukul 2 , Kullathorn Thephamongkhol 2 , Pittaya Dankulchai 2 1 Obstetrics - Gynaecology, Faculty of Medicine Siriraj Hospital, Mahidol University, Bangkok, Thailand. 2 Radiation Oncology, Faculty of Medicine Siriraj Hospital, Mahidol University, Bangkok, Thailand Purpose/Objective: This study aimed to compare clinical outcomes between adjuvant chemotherapy (CT) alone and combined CT and radiation therapy (CRT) in stage III endometrial cancer patients. Specifically, all patients received six cycles of CT before radiation therapy was initiated. This approach minimizes delays in systemic treatment and provides adequate CT dosing before RT. Additionally, the study sought to identify patient subgroups that might benefit most from adding adjuvant RT. Material/Methods: From 2007 to 2019, 181 patients with stage III endometrial cancer were included. Propensity score matching balanced baseline characteristics between groups, accounting for age-adjusted Charlson Comorbidity Index, depth of myometrial invasion, pathological grade, lymphovascular space invasion (LVSI), adnexal involvement, and FIGO 2009 stage. The final cohort comprised 118 patients (59 patients in each group: CT alone vs. CRT). The primary endpoint was pelvic recurrence; the secondary endpoints were progression-free survival (PFS) and overall survival (OS). We conducted exploratory subgroup analyses stratifying patients by stage, histological grade, lymphovascular Keywords: Cervical cancer, ovarian transposition, pelvic RT 831