ESTRO meets Asia 2024 - Abstract Book

S155

Interdisciplinary – Haematology

ESTRO meets Asia 2024

University Malaya Medical Centre experience using VMAT for total body irradiation

Nisha Shariff 1 , Aik Hao Ng 1,2 , David Dai Wee Lee 1,2 , Munira Rejab 1 , Ngie Min Ung 1,2 , Zulaikha Jamalludin 1,2 , Muhammad Zul Fadzly Mohamed Nor Mala Shasuddin 1 , Khairi Nur Nizam Samam 1 , Atiqah Kadri 1 , Nurain Suhairah Mohmad Kassim 1 , Nor Akma Shawatie Che Ab Hamid 1 , Nur Diyana Afrina Mohd Hizam 2 , Sakuntala Jagabattuni 2 , Salma Shaharudin 1 , Gwo Fuang Ho 2 1 Department of Clinical Oncology, University Malaya Medical Centre, Kuala Lumpur, Malaysia. 2 Faculty of Medicine, University Malaya, Kuala Lumpur, Malaysia

Purpose/Objective:

Total body irradiation (TBI) is a modality for conditioning prior to bone marrow transplant and has been shown to have survival benefits over chemo-conditioning in acute lymphoblastic leukaemia 1 . The delivery of TBI with conventional methods in modern radiotherapy centres is limited by the availability of sophisticated accessories and smaller bunker sizes. Advanced radiotherapy techniques offer the benefits of better patient comfort, delivery of a more homogenous dose distribution, sparing of organs at risk and easier accessibility in centres with standard linear accelerators 2 . This paper aims to report the UMMC’s experience in utilising volumetric modulated arc therapy (VMAT) technique to deliver total body irradiation using standard linear accelerators.

Material/Methods:

We started the delivery of TBI using volumetric modulated arc therapy (VMAT) in October 2023 after six months of planning and quality assurance processes. Acquisition of 3D simulation images was done with a Philips Brilliance CT simulator with the patient lying supine in a knee-bent position on a vacuum immobilisation cushion, headrest and thermoplastic shell. Two sets of images were acquired, head-first-supine (HFS) and feet-first-supine (FFS). These two image sets were imported and stitched using the MIM Maestro® version 7.0.6. TBI planning was done on Monaco version 6 treatment planning system. Treatment delivery was done with the Elekta VersaHD linear accelerator. Pre-treatment verification and patient-specific quality assurance (PSQA) were performed prior to treatment using a two-dimensional detector array MatriXX Evolution and Gafchromic EBT3 film. During treatment delivery, fast cone-beam CT (CBCT) was done for all isocentres and online correction was applied for vertical and lateral shift and a set-up error analysis was done. Longitudinal shift was corrected for the site of origin only in the pelvis. Target volume and organ at risk dose constraints were based on the ESTRO-SIOPE consensus 3 . Treatment outcomes and side effects of the patients were monitored post-treatment delivery.

Results:

We have treated five patients – four paediatric and one young adult. Patients ranged from 5 to 40 years of age. Most patients received 1200 cGy in 6 fractions over three days while one patient received 770 cGy in one fraction. All TBI treatments were given as part of conditioning for acute lymphoblastic leukaemia patients. Two patients required general anaesthesia for treatment.

Number of isocentres for all treatment plans ranged from 6 to 7. Mean numbers of monitor units were 3196 for HFS and 1615 for FFS. Optimisation statistics are displayed in Figure 1.