ESTRO 2025 - Abstract Book

S265

Brachytherapy - Gynaecology

ESTRO 2025

3489

Digital Poster Change of practice in MR-guided adaptive brachytherapy for cervical cancer by a multiparametric dose prescription protocol: From EMBRACEI to EMBRACEII Nicole Eder-Nesvacil 1 , Stefan Ecker 1 , Kari Tanderup 2 , Richard Pötter 1 , Astrid De Leeuw 3 , Maximilian Schmid 1 , Johannes Knoth 1 , Taran Paulsen-Hellebust 4 , Petra Kroon 3 , Monica Serban 5 , Sofia Spampinato 6 , Alina Sturdza 1 , Barbara Segedin 7 , Henrike Westerveld 6 , Geetha Menon 8 , Margit Valgma 9 , Laura Velema 10 , Max Peters 3 , Kathrin Kirchheiner 1 , Supriya Chopra 11 , Remi Nout 6 , Ina Jürgenliemk-Schulz 3 , Jacob Lindegaard 2 , Christian Kirisits 1 1 Department of Radiation Oncology, Medical University of Vienna, Vienna, Austria. 2 Department of Oncology, Aarhus University Hospital, Aarhus, Denmark. 3 Department of Radiation Oncology, University Medical Centre Utrecht, Utrecht, Netherlands. 4 Department of Oncology, Oslo University Hospital, Oslo, Norway. 5 Radiation Medicine Program, Princess Margaret Cancer Center, Toronto, Canada. 6 Department of Radiotherapy, Easmus MC Cancer Institute, Rotterdam, Netherlands. 7 Department of Radiotherapy, Institute of Oncology Ljubljana, Ljubljana, Slovenia. 8 Department of Oncology, Cross Cancer Institute and University of Alberta, Edmonton, Canada. 9 Department of Radiotherapy, North Estonia Medical Centre Foundation, Tallinn, Estonia. 10 Department of Radiation Oncology, Leiden University Medical Center, Leiden, Netherlands. 11 Department of Radiation Oncology, Tata Memorial Center, Mumbai, India Purpose/Objective: The EMBRACEII study (NCT03617133) defined a prospective dose prescription protocol, with major hypotheses on achievability of increased use of an intracavitary-interstitial (IC/IS) technique to deliver high target doses while simultaneously de-escalating OAR doses compared to EMBRACEI. Increased IC/IS application was expected to improve dosimetric outcome for challenging target volumes, particularly those with extensive lateral disease. This investigation aimed to analyse BT implementation and variations in treatment technique and dose between both studies, with focus on parametrial disease at time of BT. Material/Methods: Data on disease status at time of BT, BT-treatment and DVH were extracted from EMBRACEI (n=1318) and EMBRACEII (n=1376) databases. Descriptive statistics were performed for overall cohorts, and subgroups according to parametrial extension of CTV-T HR assessed on MRI at time of BT. Results: Median overall treatment time (EBRT+BT) was 46 (IQR 42,50) days in EMBRACEI and 43 (40, 46) in EMBRACEII. HDR was used in 57% and 70% EMBRACEI/EMBRACEII. Two or four BT implants were most frequent for HDR patients, with 43%/12% in EMBRACEI, vs. 54%/23% in EMBRACEII. Most patients had four or three BT fractions (EMBRACEI: 70%/22%, EMBRACEII: 80%/20%). For PDR, two implants (50%/63%) and two fractions (48%/66%) were reported in EMBRACEI/EMBRACEII. IC/IS was used for 43% in EMBRACEI and 74% in EMBRACEII. Median number of needles was 4 (2,6) in both studies. CTV-T HR D90 increased from 90 (85, 94) to 92 (91,95) Gy EQD2 10 in EMBRACEII. 83% vs. 99% of CTV-T HR <30cm³ and 66% vs. 94%>30cm³ had a D90>85 Gy in EMBRACEI/II. Table 1 shows dosimetric results for targets and OAR.