Dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI) has been provided for noninvasive assessment of different grade of gliomas. But the diagnostic performance of this new approach was variant among the recent reports. This study included 10 DCE-MRI studies regarding to differentiating high grade gliomas (HGGs) from low grade gliomas (LGGs). The meta-analysis results demonstrated that parameters of DCE-MRI have high diagnostic performanc (Ktrans and Ve) in distinguishing HGGs from LGGs. DCE-MRI can be used as an important tool for the assessment of neovascular permeability and for the pre-operative grading of glioma.
A flow diagram of the study selection is shown in Fig 1. 10studies[2,7-15]were included in our study. QUADAS-2 was used to assess the quality of each studies(Fig 2).385 patients were included (129 LGGs and 256 HGGs) Table 1.The various indicators obtained directly or indirectly from each study were shown in Table 2.Ktrans(sensitivity/specificity:I2=36.4%/3.3%, Chi-square test P=0.1176/0.4090, Fig 3A-3C) and Ve(sensitivity/ specificity: I2 =48.2%/25.5%, Chi-square test P = 0.0722/0.2345,Fig3D-3F) parameters have no heterogeneity, the pooled sensitivity /specificity are 0.90 (95% CI: 0.86 to 0.94)/0.86 (95% CI: 0.79 to 0.92) and 0.90 (95% CI: 0.84 to 0.94) / 0.86 (95% CI: 0.77 to 0.92). The AUC(SROC analysis) of Ktrans and Ve are 0.9376 (SE = 0.0178) and 0.9411 (SE = 0.0214). There are three kinds of pharmacokinetic models among included studies(Tofts model, Tofts and Kermode and Modified Tofts.Table 1).
There were no obvious threshold effect of Ktrans (Spearman correlation coefficient= 0.212,P-value= 0.556) and Ve (Spearman correlation coefficient= 0.357, P-value= 0.432).There was no significant publication bias (The Deeks’ funnel plot asymmetry test :P=0.85 for Ktrans;p=0. 22 for Ve).
DCE-MRI provides more truthful tumor perfusion information, Ktrans and Ve are the most important quantitative parameters, which showed high diagnostic performance in this meta-analysis. Our findings are also consistent with these previous studies, therefore ,DCE-MRI would contribute greatly to various clinical situations.
However, there exists some limitations about this method. The main limitation of DCE-MRI is that, at present, there is no standardization as to the optimal method of assessing perfusion[16], for example, the physiological meaning of Ve has been defined as “leakage space” in an initial study and as extravascular extracellular space or its volume in later studies[2], T1 time, cut-off value and pharmacokinetic model are different during included studies[2,7-15]. These may exist heterogeneity and the results may untruthfulness. Nevertheless , the basic theory of methods were similar, the resultant error is not so large during closely acquisition times[2]. When using different DCE protocol for grading gliomas, parametric errors occur in the same direction, their resulting distributions could be unchanged and diagnostic utility is preserved. Therefore, our results are credible and valuable, meanwhile ,further investigation involving radiological-pathological correlation is needed to determine a standard in using DCE-MRI, in order to spread DCE-MRI to clinical practice.
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