ESTRO 2025 - Abstract Book

S282

Brachytherapy - Gynaecology

ESTRO 2025

4542

Digital Poster Correlation of Indirect Ratio of Excess dose (iRex) on Late GI Tox in Cervix IGABT: A Pooled Data from single center EMBRACE II and HYPOCx-iRex study Tissana Prasartseree 1 , Sirapob Seksunwiriya 2 , Soponvit Wattanakul 2 , Tewpaithong Rodwong 2 , Wasawat Jirasuviboon 2 , Peerakarn Charoenwong 2 , Nonpawit Suriyanusorn 2 , Wiwatchai Sittiwong 1 , Pittaya Dankulchai 1 1 Division of Radiation Oncology, Department of Radiology, Faculty of Medicine, Siriraj Hospital, Mahidol University, Bangkok, Thailand. 2 Faculty of Medicine, Siriraj Hospital, Mahidol University, Bangkok, Thailand Purpose/Objective: Indirect Ratio of Excess dose volume (iRex) was definied as isodose surface volume (ISV) divided by toxicity negligible volume (Vneg) to act as a conformal constraint during brachytherapy optimization (DOI: 10.5114/jcb.2020.100377). This study aimed to assess the correlation of “iRex60” on late gastrointestinal (GI) toxicity in patients with cervical cancer treated with definite radiotherapy. This analysis is a pooled data from single-institute EMBRACE II and HYPOCx-iRex trials. Material/Methods: The study analyzed data to assess the relationship between and GI toxicity outcomes. Eligible patients included those enrolled in single-center the EMBRACE II (28 patients) and HYPOCx-iRex trial (40 patients). Toxicity was graded using the Common Terminology Criteria for Adverse Events (CTCAE) version 5.0 and were recorded at regular intervals throughout treatment and follow-up. Patient demographics, tumor characteristics, radiotherapy parameters, and toxicity outcomes were collected. Descriptive statistics were used to summarize patient and treatment characteristics. Kaplan-Meier survival analysis and Cox regression were utilized to assess cumulative toxicity and dose parameter correlation.

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