NIMG-23. COMBINATION OF ADC MRI AND FET PET FOR THE ASSESSMENT OF QUANTITATIVE TUMOR PRESENCE IN DIFFUSE GLIOMA

Abstract

Abstract BACKGROUND Local treatment of diffuse glioma is currently guided by standard MRI sequences. Yet, the combination of apparent diffusion coefficient (ADC) and O-(2-[18F]-fluoroethyl)-L-tyrosine positron emission tomography (FET PET) (ADC/FET) detects qualitatively assessed histopathological tumor presence more accurately than standard MRI imaging. It is unknown whether this is similar for quantitatively assessment of tumor presence. This study compares the diagnostic accuracy of standard imaging and ADC/FET for detecting quantitatively assessment of tumor presence in diffuse glioma. METHODS Fifteen patients with newly diagnosed diffuse glioma were retrospectively included. Pre-operative MRI and FET PET imaging were available. Multiregional image-guided stereotactic biopsies were acquired before craniotomy. Quantitative imaging data from regions-of-interests (ROIs) centered at the biopsy locations was obtained. For each biopsy sample, semi-automatic cellularity and proliferation index, as well as DNA methylation-based tumor purity, was determined. Linear mixed models were used to evaluate which modalities were significant independent predictors for each tumor presence marker, and fitness was assessed using Bayesian Information Criterium. RESULTS 125 biopsies were analyzed (75 from eight high grade and 50 from seven low grade gliomas). Cellularity was associated with T1 weighted MRI (p = 0.033), ADC (p = 0.016) and ADC/FET (p < .001), with ADC/FET as best fit. ADC/FET was the only modality associated with proliferation index (p = 0.003) and with tumor purity (p < .001). CONCLUSION Combined ADC and FET PET is stronger associated with cellularity, proliferation index and tumor purity than standard MRI imaging. These findings may pave the way towards ADC/FET-guided local treatment of diffuse gliomas.