Distinguishing recurrent high-grade gliomas from radiation injury: a pilot study using dynamic contrast-enhanced MR imaging.

RATIONALE AND OBJECTIVES The accurate delineation of tumor recurrence and its differentiation from radiation injury in the follow-up of adjuvantly treated high-grade gliomas presents a significant problem in neuro-oncology. The aim of this study was to investigate whether hemodynamic parameters derived from dynamic contrast-enhanced (DCE) T1-weighted magnetic resonance imaging (MRI) can be used to distinguish recurrent gliomas from radiation necrosis. MATERIALS AND METHODS Eighteen patients who were being treated for glial neoplasms underwent prospectively conventional and DCE-MRI using a 3T scanner. The pharmacokinetic modelling was based on a two-compartment model that allows for the calculation of K(trans) (transfer constant between intra- and extravascular, extracellular space), v(e) (extravascular, extracellular space), k(ep) (transfer constant from the extracellular, extravascular space into the plasma), and iAUC (initial area under the signal intensity-time curve). Regions of interest (ROIs) were drawn around the entire recurrence-suspected contrast-enhanced region. A definitive diagnosis was established at subsequent surgical resection or clinicoradiologic follow-up. The hemodynamic parameters in the contralateral normal white matter, the radiation injury sites, and the tumor recurrent lesions were compared using nonparametric tests. RESULTS The K(trans), v(e), k(ep), and iAUC values in the normal white matter were significantly different than those in the radiation necrosis and recurrent gliomas (0.01, <P < .0001). The only significantly different hemodynamic parameter between the recurrent tumor lesions and the radiation-induced necrotic sites were K(trans) and iAUC, which were significantly higher in the recurrent glioma group than in the radiation necrosis group (P ≤ .0184). A K(trans) cutoff value higher than 0.19 showed 100% sensitivity and 83% specificity for detecting the recurrent gliomas, whereas an iAUC cutoff value higher than 15.35 had 71% sensitivity and 71% specificity. The v(e) and k(ep) values in recurrent tumors were not significantly higher than those in radiation-induced necrotic lesions. CONCLUSIONS These findings suggest that DCE-MRI may be used to distinguish between recurrent gliomas and radiation injury and thus, assist in follow-up patient management strategy.