ESTRO 2025 - Abstract Book

S257

Brachytherapy - Gynaecology

ESTRO 2025

Material/Methods: In this phase 3, randomized, parallel-controlled trial (NCT 05690906) conducted across 9 medical centers in China from July 2022 to October 2024, 100 cervical cancer patients were enrolled, randomly assigned in a 1:1 ratio to the experimental group or control group. All patients were received concurrent chemoradiotherapy, the experimental group was received a 10mL PEG hydrogel injection after external beam radiotherapy, while the control group had no injection. Followed by image-guided adaptive brachytherapy, and the doses of rectum, sigmoid, bladder, small intestine were recorded. The Common Terminology Criteria for Adverse Events was used to evaluate side effects. The primary endpoint was the cumulative D2cc of rectum. Secondary endpoints included: cumulative doses for rectal D0.1cc, D5cc, and D2cc of sigmoid, bladder, small intestine; changes in the perirectal space and the volume of the hydrogel; quality of life scores by QLQ-C30 and QLQ-CX24; incidence of radiation-induced acute rectal injury. Results: A total of 94 patients were included, with 45 in the experimental group and 49 in the control group, 6 patients were discharged. The experimental group demonstrated a significant reduction in rectal D2cc, D0.1cc, and D5cc compared to the control group (64.23±6.58Gy vs 69.79±6.10Gy, p<0.0001; 74.67±12.22Gy vs 84.38±9.91Gy, p<0.0001; 60.23±4.96Gy vs 63.18±5.04Gy, p=0.0003), with no significant changes in doses to the small intestine, sigmoid, or bladder (78.48±6.43Gy vs 81.11±7.89Gy, p=0.091; 62.99±5.38Gy vs 63.73±5.45Gy, p=0.586; 65.75±10.89Gy vs 65.51±10.19Gy, p=0.395). The distance between the cervix or tumor margins and the rectum, as well as the minimum cervical-to-rectal distance, significantly increased during brachytherapy in the experimental group (all p values ＞ 0.05). Hydrogel volume remained stable during treatment and 24 weeks after radiotherapy, with noticeable absorption between weeks 24 and 36. No significant differences were observed between groups in the incidence of acute radiation-induced rectal injury or QLQ scores at any time point (all p value ＞ 0.05), except for higher constipation scores in the experimental group (p=0.003). The overall incidence of systemic adverse events did not differ significantly between groups. Conclusion: Injection of medical hydrogel effectively reduces rectal dose during cervical cancer brachytherapy without increasing doses to other organs at risk and maintains acceptable safety. Further follow-up is needed to explore the long-term clinical benefits.

Keywords: Polyethylene Glycol Hydrogel, Cervical Cancer

3239

Digital Poster Integrating functional MR for target volume delineation in Image guided brachytherapy of Ca Cervix Ankita - Mehta 1 , Adarsh - Hegde 2 , Jayashree NP 1 , Umesh Vellu 1 , Anshul Singh 1 , Vijayakumar Srinivasan 1 , Shirley Lewis 1 1 Radiation Oncology, Kasturba Medical College, Manipal, Manipal, India. 2 Radiodiagnosis, Kasturba Medical College, Manipal, Manipal, India Purpose/Objective: Target delineation in MR based IGABT in cervical cancers is based on the hyperintense and intermediate sig. In addition to the standard T2 sequence, functional MR imaging with DWI has led to investigations of its potential in differentiating tumor from edema based on the cellularity. This emphasizes the need to study the incremental value of incorporating DWI/ADC compared to T2 for improving the accuracy of target volume delineation in IGBT.