DCE and DSC perfusion MRI acquisition: diagnostic accuracy during the follow-up of the primary and metastatic intra-axial brain tumors treated by Stereotactic RadioSurgery performed with CyberKnife

Distinguishing radiation necrosis from tumor recurrence and tumor progression is crucial for the evaluation of treatment response and treatment planning. The appearance of treatment-induced tissue necrosis on conventional Magnetic Resonance Imaging (MRI) are very similar to brain tumor recurrence and it could be difficult to differentiate the two entities during the follow-up MRI examinations. Dynamic Susceptibility Contrast-enhanced (DSC) and Dynamic Contrast-Enhanced (DCE) are the MRI perfusion techniques using an exogenous, intravascular, no diffusible gadolinium-based contrast agent. The aim of this study is to compare the diagnostic accuracy of DSC and DCE perfusion MRI in the differential diagnosis between radiation necrosis and tumor recurrence, in the follow-up of the primary and metastatic intra-axial brain tumors after Stereotactic RadioSurgery (SRS) treatment performed with CiberKnife. A total of 72 enhanced lesions (57 brain metastases and 15 primary brain tumors) were studied. The statistical analysis showed a correlation between the diagnosis of radiation necrosis or recurrent tumor and Ktrans (rpb=0.54, p<0.001) and of the diagnosis with rCBV(rpb=0.37, p=0.002). The ROC analysis of rCBV values demonstrated a good classification ability in differentiating radiation necrosis from tumour recurrence as soon as the Ktrans. The optimal cut-off value for rCBV was k=1.23 with 0.88 of sensitivity and 0.75 of specificity while for Ktrans was k=28.76 with 0.89 of sensitivity and 0.97 of specificity. The use of DCE and DSC alone, better DCE if available, can help in the differential diagnosis by tumor recurrence and radiation necrosis during the follow-up.