ESTRO 2025 - Abstract Book

S856

Clinical - Gynaecology

ESTRO 2025

3426

Proffered Paper Risk factors for acute gastrointestinal toxicity in cervix cancer treated with advanced image-guided radiochemotherapy: an EMBRACE-II analysis. Mayuri S Charnalia 1 , Sofia Spampinato 2 , Richard Pötter 3 , Marta Pelizzola 1 , Ina M Jurgenliemk-Schulz 4 , Maximilian P Schmid 3 , Kjersti Bruheim 5 , Barbara Segedin 6,7 , Jacob C Lindegaard 8 , Ericka Wiebe 9 , Henrike Westerveld 10,11 , Margit Valgma 12 , C. (Cornelia) G Verhoef 13 , Li Tee Tan 14 , Hanne F Mathiesen 15 , Christian Kirisits 3 , Monica Serban 16,17 , Jeevanshu Jain 18 , Kathrin Kirchheiner 3 , Anna K Clark 19 , Remi A Nout 2 , Supriya Chopra 18 , Kari Tanderup 1,20 1 Danish Centre for Particle Therapy, Aarhus University Hospital, Aarhus, Denmark. 2 Department of Radiotherapy, Erasmus MC Cancer Institute, Rotterdam, Netherlands. 3 Department of Radiation Oncology, Comprehensive Cancer Center, Medical University of Vienna, Vienna, Austria. 4 Department of Radiation Oncology, University Medical Centre Utrecht, Utrecht, Netherlands. 5 Department of Oncology, Oslo University Hospital, Oslo, Norway. 6 Department of Radiotherapy, Institute of Oncology, Ljubljana, Slovenia. 7 Faculty of Medicine, University of Ljubljana, Ljubljana, Slovenia. 8 Department of Oncology, Aarhus University Hospital, Aarhus, Denmark. 9 Department of Oncology, Cross Cancer Institute, University of Alberta, Edmonton, Canada. 10 Department of Radiation Oncology, Amsterdam UMC Location of University of Amsterdam, Amsterdam, Netherlands. 11 Department of Radiotherapy, Erasmus MC Cancer Institute, University Medical Center Rotterdam, Rotterdam, Netherlands. 12 Radiotherapy Centre, North Estonia Medical Centre Foundation, Tallinn, Estonia. 13 Department of Radiotherapy, Radboud university medical center, Nijmegen, Netherlands. 14 Oncology Centre, Cambridge University Hospitals NHS Foundation Trust, Cambridge, United Kingdom. 15 Department of Oncology, Rigshospitalet, Copenhagen, Denmark. 16 Radiation Medicine Program, Princess Margaret Cancer Centre, Toronto, Canada. 17 Department of Radiation Oncology, University of Toronto, Toronto, Canada. 18 Department of Radiation Oncology, Advanced Centre for Treatment Research and Education in Cancer, Tata Memorial Centre, Homi Bhabha National Institute, Navi Mumbai, India. 19 Department of Medical Physics, Leeds Cancer Centre, Leeds, United Kingdom. 20 Department of Clinical Medicine, Aarhus University, Aarhus, Denmark Purpose/Objective: To identify risk factors associated with acute gastrointestinal (GI) toxicity occurring during external beam radiotherapy (EBRT) and concomitant chemotherapy course in locally advanced cervical cancer (LACC) patients. Material/Methods: Data from the international, prospective, multi-institutional, interventional EMBRACE-II study (2016-2021) were analysed. Patients received image-guided intensity-modulated radiotherapy/volumetric arc therapy, concurrent chemotherapy, and MRI-guided adaptive brachytherapy. EBRT used highly conformal dose distributions achieved with IMRT/VMAT and daily cone-beam computed tomography including coverage probability planning [1] for simultaneously integrated nodal boosts. EBRT prescription dose was 45Gy/25 fractions and 55-65Gy EQD2 10 recommended for positive lymph nodes, as per institutional practice. To infer impact of EBRT, physician-assessed (CTCAEv.3) acute GI toxicity (diarrhea, abdominal pain/cramping, proctitis, fecal urgency: inability to defer defecation>15min) at 4 th week of treatment (RT4W) was evaluated. Patient-, disease-, EBRT-related parameters were tested as risk factors. Univariate (UVA) and multivariable (MVA) logistic regression was applied to incidence of moderate-to-severe (G≥2) GI toxicity. Correlation of continuous variables significant in UVA (p<0.05) was evaluated with Pearson coefficient (r). Variable with highest clinical relevance and r≥0.25 was included in MVA. To identify risk factors, stepwise backward logistic regression was performed. Akaike Information Criterion (AIC) was used as stopping rule, and model with lowest AIC was selected. Results: 1334 patients with availability of GI toxicity assessment at RT4W were included in analysis. Incidences of G≥2 diarrhea, abdominal pain/cramping, and proctitis at RT4W was 16% (n=212), 6% (n=85), and 2% (n=30), respectively. Incidence of fecal urgency was 25% (n=332). Predictive patient characteristics were: age, smoking status, body-mass index, comorbidity, previous pelvic/abdominal surgery, baseline GI symptoms. Predictive treatment parameters were: bowel volume receiving 40Gy (bowel V40Gy), body volume receiving 50Gy (body V50Gy) from lymph node