IMG-34. THE UTILITY OF [18F]FET PET IMAGING IN PAEDIATRIC CNS TUMOURS: A SINGLE INSTITUTION EXPERIENCE IN SYDNEY, AUSTRALIA Open Access

MRI remains the standard imaging modality in paediatric CNS tumours. Whilst Positron emission tomography (PET) with O-(2-[18F]fluoroethyl)-L-tyrosine ([18F-FET) is a well-established tool in adult central nervous system (CNS) tumours, established data on its diagnostic utility and impact on clinical management in children and adolescents remain limited.

Single centre retrospective review of database of all paediatric and adolescent patients (age 0-19years) who underwent ¹⁸F]FET-PET imaging with cross referencing of patient electronic medical records. Conducted at the Children’s Hospital at Westmead in Sydney, Australia.

116 patients underwent ¹⁸F-FET PET imaging between October 2012 and January 2024. 28 patients had additional comparative fluorodeoxyglucose (FDG) CNS dedicated PET imaging. Primary indications for FET PET imaging included differentiating between a neoplastic versus non-neoplastic process (23.3%), identifying active residual tumour (14.7%), characterising tumour grade in patients including in those with the known tumour predisposition syndromes (6%), distinguishing between progression pseudo-progression (2.5%) and providing additional localisation or biopsy guidance (8.6%). Malignant transformation, gliomatosis and extent of disease was also noted as indications. 15 patients were able to avoid a biopsy or invasive surgery. Nearly 60% of FET PET imaging was considered clinically useful with the management of 52/112 (46%) patients being supported or changed. Management changes included change second look surgery, change of radiation field, change of treatment and access to a clinical trial. Only 3 scans were reported to have technical challenges in resolution or poor spatial correlation with MRI. Further analysis is currently being conducted, reviewing standard uptake values (SUV’s) of histologically proven low/high grade tumours and T2 enhancing/non-enhancing lesions.

This small study demonstrated the clinical benefit and utility of ¹⁸F-FET PET imaging in paediatric CNS tumours. Our experience has demonstrated significant surgical and diagnostic advantage in tumour localisation as well as avoiding surgery where able.