Js09.7.a combination of apparent diffusion coefficient and fet pet compared with standard imaging for quantitative tumor presence in diffuse gliomas

Abstract BACKGROUND Diffuse glioma local treatment 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 histopathological qualitative assessed tumor presence more accurately than standard imaging. It is unknown whether this is similar for quantitative assessed tumor presence. This study compares the diagnostic accuracy of standard imaging and ADC/FET for the detection of quantitative assessed tumor presence in diffuse glioma. MATERIAL AND METHODS Fifteen patients with newly diagnosed diffuse glioma were retrospectively included. Pre-operative standard imaging, ADC and FET PET 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 predicted by T1 weighted MRI (p = 0.033), ADC (p = 0.016) and ADC/FET (p <.001), with ADC/FET as best fit. Both proliferation index (p = 0.003) and tumor purity (p <.001) were only predicted by ADC/FET. CONCLUSION Combining ADC and FET PET predicts cellularity, proliferation index and tumor purity better than standard imaging. Further investigation into ADC/FET-guided local treatment of diffuse glioma is therefore needed.