S75
Brachytherapy - Gynaecology
ESTRO 2026
2 Department of Medical Physics, Pamela Youde Nethersole Eastern Hospital, Hong Kong, Hong Kong
morbidity. None of the patients had grade 3 or higher toxicity or vaginal stenosis. No patient developed fistula during or post treatment
Purpose/Objective: Magnetic resonance-image guided adaptive
brachytherapy (MR-IGABT) has shown to improve therapeutic ratio and clinical outcomes, and is standard of care for locally advanced cervical cancer (LACC)1. Despite its clear benefits, MR-IGABT is often underutilized in areas with high disease prevalence. This study reports on 10-year institutional experience in MR-IGABT for Chinese patients, including outcomes from different periods of technique development. Material/Methods: Consecutive patients with LACC received MR-IGABT between January 2015 and June 2025 were included. Patients received external beam radiotherapy (EBRT) 45Gy in 25 fractions with concurrent weekly cisplatin, followed by 4 fractions of HDR MR-IGABT delivered over 2 weeks. Brachytherapy prescription followed GEC-ESTRO recommendations2. Institutional treatment standards were refined in April 2019 to follow the EMBRACE-II protocol3. Primary outcomes were local control (LC), pelvic control (PC) and cancer- specific survival (CSS). Toxicity was graded by CTCAE v5.0. Treatment characteristics and outcomes in early years of MR-IGABT practice (2015-March 2019) vs later years (since April 2019) were compared. Results: Median follow-up was 46.0 months for 218 patients identified. Median age was 57. 94% had ECOG PS 0-1. 80.3% had squamous cell carcinoma. FIGO2018 stage was IB-IIA 6.5%, IIB 32.1%, IIIA-IIIB 5.1%, IIIC1 39.0%, IIIC2 12.8%, and IVA 3.2%. Median primary tumour width was 51.5mm. 87.9% received concurrent cisplatin. Patients treated in later years of MR-IGABT practice had significantly higher proportion of FIGO IIIC2 (17.1% vs 3.0%), VMAT EBRT (99.3% vs 16.7%), and shorter overall treatment time (44 vs 46 days). Cumulative GTVD98 and HRCTVD90 were significantly higher in later years (p<0.001), in addition to lower rectal and bowel D2cc, and vaginal TRAK, related to systematic application of interstitial techniques (Table 1). Actuarial estimates for LC, PC, CSS and overall survival (OS) were 91%, 88%, 90% and 89%, respectively, at 3 years, and 91%, 85%, 82%, and 78% at 5 years (Figure A). A trend towards better CSS was observed in patients treated in later years, and statistical significance was detected after adjustment for FIGO stage (p=0.045; Figure B). Cumulative incidence of grade 2 or above and grade 3 late gastrointestinal toxicity was 8.7% and 1.8%, respectively, and 6.0% and 2.3% for genitourinary events (Figure C). Among several predictors, HRCTVD90 was associated with LC and OS, and HRCTV/ IRCTV volumes with LC, PC, and locoregional control (Figure
Conclusion: This is one of the first study reporting outcome data in locally advanced vaginal recurrences treated using GEC-ESTRO (ACROP)–ABS–CBGguidelines. Our initial results of MR interstitial brachytherapy following these consensus guidelines show optimal local control with minimal toxicity in a very advanced stage population. Further studies with longer follow up are required to establish long term outcomes and validate the guidelines Keywords: Vaginal cancer, MR interstitial brachytherapy References: GEC-ESTRO (ACROP)–ABS–CBG Consensus Brachytherapy Target Definition Guidelines for Recurrent Endometrial and Cervical Tumors in the Vagina. Kamrava, Mitchell et al.International Journal of Radiation Oncology, Biology, Physics, Volume 115, Issue 3, 654 – 663 MR-IGABT for locally advanced cervical cancer in Hong Kong: long term institutional outcomes from a decade of evolution in radiotherapy standards Philip Y Wu 1 , Frederick CH Law 2 , Elki SN Cheung 1 , William WL Wong 1 , Kelvin YC Zheng 1 , Inda S Soong 1 , Ken KS Wong 1 , Jasmine M Wong 2 , Hing Ming Hung 1 , Nelson TC Fung 2 1 Department of Clinical Oncology, Pamela Youde Nethersole Eastern Hospital, Hong Kong, Hong Kong. Digital Poster 3664
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