Antiangiogenic therapy is a universal approach to the treatment of malignant gliomas but fails to prolong the overall survival of newly diagnosed or recurrent glioblastoma patients. Imaging biomarkers are quantitative imaging parameters capable of objectively describing biological processes, pathological changes and treatment responses in some situations and have been utilized for outcome predictions of malignant gliomas in anti-angiogenic therapy. Advanced magnetic resonance imaging techniques (including perfusion-weighted imaging and diffusion-weighted imaging), positron emission computed tomography and magnetic resonance spectroscopy are imaging techniques that can be used to acquire imaging biomarkers, including the relative cerebral blood volume (rCBV), Ktrans, and the apparent diffusion coefficient (ADC). Imaging indicators for a better prognosis when treating malignant gliomas with antiangiogenic therapy include the following: a lower pre- or post-treatment rCBV, less change in rCBV during treatment, a lower pre-treatment Ktrans, a higher vascular normalization index during treatment, less change in arterio-venous overlap during treatment, lower pre-treatment ADC values for the lower peak, smaller ADC volume changes during treatment, and metabolic changes in glucose and phenylalanine. The investigation and utilization of these imaging markers may confront challenges, but may also promote further development of anti-angiogenic therapy. Despite considerable evidence, future prospective studies are critically needed to consolidate the current data and identify novel biomarkers.
Keywords: 18F-FDOPA, 3,4-dihydroxy-6-[18F]-fluoro-l-phenylalanine; 18F-FLT, [18F]-fluoro-3-deoxy-3-L-fluorothymidine; ADC, apparent diffusion coefficient; AVOL, arterio-venous overlap; Anti-angiogenic; BBB, blood brain barrier; Biomarkers; CBF, cerebral blood flow; CBV, cerebral blood volume; CNS, central nervous system; CT, computed tomography; D-2HG, D-2-hydroxypentanedioic acid; DCE-MRI, dynamic contrast-enhanced magnetic resonance imaging; DSC-MRI, dynamic susceptibility contrast magnetic resonance imaging; DWI, diffusion-weighted imaging; FDG, fluorodeoxyglucose; FLAIR, fluid-attenuated inversion recovery; FSE pcASL, fast spin echo pseudocontinuous artery spin labeling; GBM, glioblastoma; Glioma; Imaging; Ktrans, volume transfer constant between blood plasma and extravascular extracellular space; MRI, magnetic resonance imaging; MRS, magnetic resonance spectroscopy; OS, overall survival; PET, positron emission computed tomography; PFS, progression-free survival; PWI, perfusion-weighted imaging; RANO, Response Assessment in Neuro-Oncology; ROI, region of interest; RSI, restriction spectrum imaging; SUV, standardized uptake value; TMZ, temozolomide; Therapy; VAI, vessel architectural imaging; VEGF-A, vascular endothelial growth factor A; VNI, vascular normalization index.; fDMs, functional diffusion maps; nGBM, newly diagnosed glioblastoma; rCBF, relative cerebral blood flow; rCBV, relative cerebral blood volume; rGBM, recurrent glioblastoma.