ESTRO meets Asia 2024 - Abstract Book

S63

Interdisciplinary – Brachytherapy

ESTRO meets Asia 2024

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Digital Poster

Mandible spacing effect in HDRIBT following IMRT (HyBIRT) for tongue squamous cell carcinoma (TSCC)

Keerthaanaa Yogabalan 1 , Muhamad Yusri Musa 1 , Ch'ng Ewe Seng 1 , Jasmin Jalil 1 , Syadwa Abdul Shukor 2 , Siti Noor Fazliah Mohd Noor 3 , Ahmad Fakrurrozi Mohamad 3 , Nor Hafizah Ishak 1 , Mohd Zahri Abdul Aziz 1 , Gokula Kumar Appalanaido 1 1 Radiotherapy Unit, Advanced Medical & Dental Institute (AMDI), Universiti Sains Malaysia, Kepala Batas, Malaysia. 2 Radiation Oncology, National University Cancer Institute, Singapore, Singapore. 3 Dental Unit, Advanced Medical & Dental Institute (AMDI), Universiti Sains Malaysia, Kepala Batas, Malaysia

Purpose/Objective:

HDRIBT followed-by IMRT (HyBIRT) technique is an organ preservation option in the definitive treatment of tongue squamous cell carcinomas (TSCC) for patients who are unfit or refuse surgery [1]. Osteoradionecrosis (ORN) is a known side effect of this treatment regimen. Mandible spacing (MS) is used to reduce the incidence of ORN. However in our series, we noticed that the ORN occurs near universally at the posterior lower mandible (PLM) at the molar and premolar region. This study looks at the HDRIBT dosimetry with MS and the ideal MS thickness by comparing the MS covered anterior part of lower mandible (ALM) to the PLM.

Material/Methods:

CT-scan based TSCC Oncentra TM brachytherapy plans of 8 patients with various MS thickness and the subsequent Monaco TM IMRT plans were analysed. The cumulative 2 Gy equivalent (EqD2) mandible dose is calculated using EqD2 formula. A 0.2 cm diameter “pearl” tool was used to contour the medial part of the adjacent mandible to the HDRIBT region which is the area of interest (AOI) for ORN occurrence and analysed. Descriptive statistics is used to present the data.

Results:

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