ESTRO 2025 - Abstract Book

S271

Brachytherapy - Gynaecology

ESTRO 2025

4053

Digital Poster Feasibility of CT-based target delineation and its influence in the intracavitary brachytherapy planning in cervical cancer. Shaha Sheik Abdulla 1 , Dillip Kumar Parida 1 , Sudipta Mohakud 2 , Saroj Kumar Das Majumdar 1 , Sandip Kumar Barik 1 , Deepak Kumar Das 1 , Sasanka Sekhar Beura 1 , Bijay Kumar Barik 1 , Anupam Muraleedharan 1 , Sk Soel Ahmed 1 , Arnab Sarkar 1 , Ankur Mahajan 1 1 RADIATION ONCOLOGY, ALL INDIA INSTITUTE OF MEDICAL SCIENCES, BHUBANESWAR, India. 2 RADIODIAGNOSIS, ALL INDIA INSTITUTE OF MEDICAL SCIENCES, BHUBANESWAR, India Purpose/Objective: In low-middle-income countries, MR-Image-guided Adaptive Brachytherapy (IGABT) availability is disproportionate to the incidence of cervical cancer, where CT is widely available and a potential alternative. We segmented the HRCTV in CT-brachytherapy imaging and correlated the factors influencing the coverage of HRCTV D90. The DVH parameters between the HRCTV manually optimized plan and the standard loading plan were also compared. Material/Methods: 32 patients from stage IIB to IVA were prospectively included. All patients received definitive Chemoradiotherapy 50Gy/25 fractions by conformal EBRT. The clinical-radiological Diagrams were documented at diagnostic as well as pre-BT, based on the IBS-GEC-ESTRO-ABS recommendation(1). After application of central Tandem & Ovoids, 7Gy/fraction was prescribed to point A, delivered weekly for a total of three fractions with OAR-optimised. Then, HRCTV was delineated in CT imaging with the help of Diagnostic MR and Pre-BT MR findings. Patients were divided into two groups: those who achieved the hard dose constraints HRCTV D90 >35GyEQD2 in brachytherapy as group 1 or those who did not achieve it as group 2. Through bivariate analysis, the factors correlated were HRCTV volume, Near Maximum Distance (NMD), and post-EBRT response. Another plan was made with manual HRCTV optimization to know the advantages in achieving hard constraints (HRCTV D90, D 2CC of bladder, rectum, and sigmoid)(2). Results: 53%(n=17) patients achieved hard constraints while 47%(n=15) did not. The mean HRCTV volume in groups 1 & 2 is 16.90cc & 29.99cc (p-<0.01). The mean NMD distance in groups 1 & 2 is 18.43cm & 22.37cm (p-0.052). Regarding post-EBRT response, the category I BT & II BT are represented equally in both groups(p-0.85). After optimization, hard constraints for HRCTV D90 increased from 53% to 69% (p-0.01) significantly, for D 2CC of the bladder (85% to 100%, p 0.062), rectum (75% to 97%, p-0.25) and sigmoid (94% to 97%, p-0.06) which influenced by volume without compromising the point A dose (figure-1).