S480
Clinical - Gynaecological
ESTRO 2026
References: Santaballa, A., et al. Multidisciplinary consensus on the criteria for fertility
benefits, and early-toxicity outcomes of daily ITV-free oART. Material/Methods: Between May-2023 and March-2025, twenty consecutive endometrial cancer patients were treated with oART. Target delineation followed published guidelines, defining nodal (CTVn) and vaginal (CTVv) clinical target volumes. ITV was created using dual CT (full and empty bladder) or via anisotropic expansion (0.2–0.7 cm) only for the standard- IMRT plan. For each patient, two plans were created: a standard IMRT plan (CTVn + 0.5 cm; ITV expansion 0.5–1.0 cm) and an adaptive plan (CTVn + 0.3 cm; CTVv + 0.5 cm; no ITV). The prescribed dose was 45–50.4 Gy in 25–28 fractions. The adaptive workflow included AI-assisted contouring, physician review, plan comparison, and a verification CBCT before delivery. Dosimetric indices and acute toxicities were prospectively recorded. Results: Median age was 66 years (range, 42–81). 90% had FIGO, 2023 stage II or III; 45% received chemotherapy, and 55% received brachytherapy boost. A total of 523 adaptive plan pairs were analyzed. Adaptive plans achieved significantly improved target coverage compared with scheduled (PTV V95: 99.7% vs 97.6%; CTVn V98: 99.5% vs 98.0%; CTVv V98: 99.7% vs 96.6%; all p<0.0001), while maintaining an acceptable Paddick conformity (0.88) and homogeneity (6.1%) indices. Bladder and rectum exposure decreased markedly. Bladder V30: 53.57% vs 54.89%, p=0.0274; V40: 31.53% vs 37.95%, p<0.0001). Adaptive planning reduced mean bladder V45 from 23.07% to 18.38% (p<0.0001). Rectal V30, V40, V50 reductions of 25.9%, 41.6%, 68.8%; all p<0.0001), and bowel V30, V40, V50 were reduced (7.7%, 22.2%, 31.5%; all p<0.0001). Median follow-up: 16 months (4–23). There were no isolated pelvic recurrences, with two patients who recurred with simultaneous nodal and distant (both IIIC1mp53abn). Acute toxicity was mild: 85% and 70% had ≤ grade 1 GU or GI toxicity; one patient had grade 3 diarrhea during
preservation in cancer patients. Clin Transl Oncol 24, 227–243 (2022).Hill-Kayser C, et al. Effects of Radiation Therapy on the Female Reproductive Tract in Childhood Cancer Survivors: A PENTEC Comprehensive Review. Int J Radiat Oncol Biol Phys. 2024 Jun 1;119(2):588-609.Gross JP, et al. Proton Radiotherapy to Preserve Fertility and Endocrine Function: A Translational Investigation. Int J Radiat Oncol Biol Phys. 2021 Jan 1;109(1):84-94.Xiao-Gang An, et al. Comparison of photon energies and field techniques for ovarian dose reduction in volumetric modulated arc therapy, Radiation Physics and Chemistry, Volume 218, 2024, 111567, ISSN 0969-806X, Keywords: AYA, fertility, particle therapy ITV-Free Online Adaptive Adjuvant Pelvic Radiotherapy for Endometrial cancer: Feasibility, Dosimetric Advantages, and Early Oncologic Outcomes. Daniel Levy, Einat Pellow, Ayman Salhab, Yair Hillman, Jon Feldman, Marc Wygoda, Aron Popovtzer, Philip Blumenfeld, Marcel Fang Sharett Institute of Oncology, Hadassah Medical Center The Hebrew University of Jerusalem, Jerusalem, Israel Purpose/Objective: Endometrial cancer is the most common gynecologic malignancy and external beam radiotherapy is a key component of adjuvant treatment. Daily online adaptive radiotherapy Poster Discussion 4119 (oART) allows plan modification based on real-time anatomy. By eliminating the need for an internal target volume (ITV), oART can account for interfractional variations in organ-at-risk (OAR) and target anatomy, potentially improving target coverage and reducing normal tissue exposure. We evaluated the clinical feasibility, dosimetric
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