The parametric response map is an imaging biomarker for early cancer treatment outcome

In this study, Galbán and his colleagues describe a voxel-wise approach for the quantification of tumor microvasculature properties from perfusion magnetic resonance imaging data. When compared to the standard method of using region of interest analysis of changes in relative cerebral blood flow and volume, the parametric response map approach was found to be more predictive of treatment outcomes and overall survival in individuals with high-grade glioma. Here we describe the parametric response map (PRM), a voxel-wise approach for image analysis and quantification of hemodynamic alterations during treatment for 44 patients with high-grade glioma. Relative cerebral blood volume (rCBV) and flow (rCBF) maps were acquired before treatment and after 1 and 3 weeks of therapy. We compared the standard approach using region-of-interest analysis for change in rCBV or rCBF to the change in perfusion parameters on the basis of PRM (PRMrCBV and PRMrCBF) for their accuracy in predicting overall survival. Neither the percentage change of rCBV or rCBF predicted survival, whereas the regional response evaluations made on the basis of PRM were highly predictive of survival. Even when accounting for baseline rCBV, which is prognostic, PRMrCBV proved more predictive of overall survival.