Abstract
In patients with high grade gliomas (HGGs), progression after treatment can be difficult to diagnose due to treatment-related effects, which overlap in appearance with tumour progression on conventional magnetic resonance imaging (MRI) sequences. Specialised imaging methods have been studied for this purpose, though most institutions currently use histopathology or clinicoradiological follow-up for diagnosis. This publication aims to review the evidence for perfusion MRI techniques. The databases of Pubmed, MEDLINE, EMBASE and Scopus were searched using combinations of the subject headings high grade glioma and MRI perfusion. 41 articles fulfilled the inclusion criteria. Dynamic Susceptibility Contrast (DSC) MRI was the most extensively studied, with several studies achieving high sensitivities and specificities. Other techniques exhibiting potential include Dynamic Contrast Enhanced (DCE) MRI, Arterial Spin Labelling (ASL). However, these techniques are not widely used or available for clinical practice. Composite measures combining results from multiple techniques tended to achieve higher accuracies. Some publications compared processing software used or looked at machine learning with relative success. An issue common to the literature is the lack of standardisation in the reference standard and acquisition/processing methods. Furthermore, many had small sample sizes, and further consideration needs to be given with regards to timing of imaging, and treatment regimens received in such studies.
Highlights
High Grade Gliomas (HGGs), accounting for approximately 50% of all gliomas, are a group of highly malignant primary brain tumours (WHO Grades III and IV) known for their poor prognosis [1]
In patients with high grade gliomas (HGGs), progression after treatment can be difficult to diagnose due to treatment-related effects, which overlap in appearance with tumour progression on conventional magnetic resonance imaging (MRI) sequences
With the addition of TMZ to the treatment regime, it is believed that up to 30% of patients will show a new or enlarging area of enhancement on conventional magnetic resonance imaging (MRI), of which up to 64% may be attributed to treatment-related effects such as pseudo progression (PsP) or radiation necrosis (RN) [4] [5] [6]
Summary
High Grade Gliomas (HGGs), accounting for approximately 50% of all gliomas, are a group of highly malignant primary brain tumours (WHO Grades III and IV) known for their poor prognosis [1]. With the addition of TMZ to the treatment regime, it is believed that up to 30% of patients will show a new or enlarging area of enhancement on conventional magnetic resonance imaging (MRI), of which up to 64% may be attributed to treatment-related effects such as pseudo progression (PsP) or radiation necrosis (RN) [4] [5] [6]. These treatment-related effects are clinically important for several reasons. The validity of phase II clinical trials for salvage therapy in recurrent gliomas has been questioned due to the false inclusion of patients with PsP who appear to respond well to the new treatment, but are instead undergoing resolution of their treatment-induced changes [7] [8] [9]
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