Img-19. Clinical Utility of Non-FDG Pet-Mri in Children With CNS Neoplasms: A Territory-Wide Study From Hong Kong

Abstract INTRODUCTION Magnetic resonance imaging (MRI) is the gold-standard for neuroimaging, yet details from anatomical scans might be inconclusive in certain scenarios. This study aimed to investigate the utility of amino-acid tracer positron emission tomography-magnetic resonance imaging (PET-MRI) based on a territory-wide Pediatric Neuro-Oncology cohort from Hong Kong. METHODS We reviewed the PET-MRI scans of pediatric patients with suspected/confirmed CNS neoplasms co-managed by Hong Kong Children’s Hospital and St. Teresa’s Hospital, Hong Kong from 5/2022-1/2024. Tracers used included C11-MET (n=10, before 5/2023) and F18-FET (n=15, in/after 5/2023). Lesion-to-normal SUVmax ratios (LNRmax) were measured with reference to adjacent or contralateral normal brain structures. RESULTS Twenty-five patients were included (M:F=13:12) with a median age of 10 years (range: 1-17). Anatomical sites of interest were the pituitary (n=13), basal ganglia (n=3), cerebellum (n=3), brainstem (n=2), frontal lobe (n=2), cerebellopontine angle (n=1), and spine (n=1). PET-MRI was performed as part of initial diagnostics in 21, to assess post-operative residual in 2, and for possible relapse in 2. Among those evaluated upfront (n=21), median SUVmax and LNRmax were 1.53 (range: 0.87-2.6) and 0.87 (range: 0.45-1.92) respectively in patients with presumed/confirmed low-grade glioneuronal (n=5) or non-oncologic lesions (n=8), versus 4.75 (range: 2.58-9.6) and 3.26 (range: 1.78-4.9) in patients with histologically/biochemically confirmed high-grade lesions (germinoma=6, high-grade glioma=2). Availability of functional PET imaging was deemed useful for scan interpretation in all 25 patients. Specifically, the use of PET-MRI facilitated decision for radiographic surveillance without biopsy/resection in 12 patients, refined tumor grading in 2 patients with discrepant clinical-histologic features, and allowed response-adapted therapy after serial scans in 5 patients. CONCLUSIONS Our study demonstrates the potential benefits of PET-MRI in the management of children with CNS pathologies. PET-MRI contributes to the diagnosis, monitoring, and treatment guidance of these patients, providing crucial information for clinical decision-making.