Fractional Anisotropy Correlates with Overall Survival in Glioblastoma. 
Glioblastoma (GB) is an infiltrative disease that results in microstructural damage on a cellular level.  Fractional anisotropy (FA) is an important estimate of diffusion tensor imaging (DTI) that can be used to assess microstructural integrity.  The aim of this study was to examine the correlation between FA values and overall survival (OS) in patients with GB.  This retrospective single-center study included 122 consecutive patients with GB (50 women; median age, 63 years) with preoperative MRI including fluid attenuated inversion recovery (FLAIR), contrast-enhanced T1-weighted sequences, and DTI.  FA and apparent diffusion coefficient (ADC) values in contrast-enhancing lesions (FA-CEL, FA-ADC), nonenhancing lesions, and central tumor regions were correlated to histopathologic and clinical parameters.  Univariate and multivariate survival analyses were performed.  Patients with low FA-CEL (median <0.31) showed significantly improved OS in univariate analysis (P = 0.028).  FA-CEL also showed a positive correlation with Ki-67 proliferation index (P = 0.003).  However, in a multivariate survival model, FA values could not be identified as independent prognostic parameters beside established factors such as age and Karnofsky performance scale score.  FA values in nonenhancing lesions and central tumor regions and mean ADC values had no distinct influence on OS.  FA values can provide prognostic information regarding OS in patients with GB.  There is a correlation between FA-CEL values and Ki-67 proliferation index, a marker for malignancy.  Noninvasive identification of more aggressive GB growth patterns might be beneficial for preoperative risk evaluation and estimation of prognosis.