ESTRO 2025 - Abstract Book

S250

Brachytherapy - Gynaecology

ESTRO 2025

Data showed there is little to no significant difference in OAR doses for 3F and 4F schedules. The HR-CTV volume was the main factor in determining the use of 3F or 4F. At one-year, local control was achieved for all 3F patients, suggesting 3F is not inferior. Our current practice is to deliver 3F, considering 4F when there is difficulty achieving adequate HR-CTV coverage whilst meeting OAR constraints.

Keywords: cervix, fractionation

References: [1] The Royal College of Radiologists. Radiotherapy dose fractionation. Fourth edition. London: The Royal College of Radiologists, 2024. [2] Scott A, Weersink M , Zhihui A et al. Comparing dosimetry of locally advanced cervical cancer patients treated with 3 versus 4 fractions of MRI-guided brachytherapy. Brachytherapy 2023; 22(2):146-156. [3] EMBRACE www.embracestudy.dk [4] Cibula D, Potter R, Planchamp F, et al. The European Society of Gynaecological Oncology/European Society for Radiotherapy and Oncology/European Society for Radiotherapy and Oncology/European Society of Pathology guidelines for the management for the management of patients with cervical cancer. In J Gynaecol Cancer 2018; 28: 641-55.

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Digital Poster Clinical outcomes of weekly versus biweekly interstitial and intracavitary brachytherapy for locally advanced cervical cancer Paramintra Chitmanee 1 , Teratat Sampaongen 2 , Nattawat Klomjit, 3 1 Radiotherapy and oncology center, Ratchaburi hospital, Ratchaburi, Thailand. 2 Ratchaburi hospital, Ratchaburi hospital, Ratchaburi, Thailand. 3 Division of Nephrology and Hypertension, Department of Medicine, University of Minnesota, Minneapolis, USA Purpose/Objective: Intracavitary and interstitial brachytherapy can enhance tumor dose coverage. The prescription dose is typically 7 Gy per fraction for 4 fractions; however, the dosing schedule remains controversial. The total treatment time may impact survival outcomes. This study aims to compare the clinical outcomes and toxicities of weekly versus biweekly interstitial and intracavitary brachytherapy in 3D image-based brachytherapy for locally advanced cervical cancer. Material/Methods: A total of 229 cervical cancer patients were treated with chemoradiation (weekly cisplatin 40 mg/m 2 combined with EBRT 45 – 50 Gy) and high-dose-rate (HDR) brachytherapy between 2017 and 2023. The prescribed dose was 7 Gy per fraction for 4 fractions. Of these, 126 patients (Group A) received weekly brachytherapy, while 103 patients (Group B) were treated with a biweekly schedule. Target delineation followed the GEC-ESTRO guidelines, with the goal of achieving a total dose of ≥ 85Gy (D90 HR-CTV) in EQD2. Results: The mean follow-up times were 34.38 months (range: 30.23–38.53) for Group A and 28.57 months (range: 25.46– 31.68) for Group B. The estimated 5-year local control rates were 82.15% for Group A and 55.96% for Group B (p = 0.318). The mean doses of D90 HR-CTV, D90 IR-CTV, D2cc bladder, D2cc rectum, D2cc sigmoid, and D2cc bowel were as follows: 90.42, 67.05, 75.24, 67.69, 63.14, and 58.83 Gy in Group A; and 91.81, 65.01, 76.42, 65.56, 65.41, and 61.42 Gy in Group B. Late grade 3 toxicities, including proctitis, cystitis, and vaginal stenosis, were observed in 7.1%/3.9% (p = 0.718), 1.6%/1.0% (p = 0.337), and 1.6%/2.9% (p = 0.588) of patients in Groups A and B, respectively.