## 3 Results
### Historical Comparison Cohort and Analysis of Outcomes  
Sixty-six patients with pathology-confirmed glioblastoma with a mean age of 59.4 (\(\pm\)12.1) years were included from the historical comparison cohort at MDACC. Compared to the primary enrollment cohort (\(n=7\)), a larger proportion of cases had right-sided (33/66, 50%) or non-cortical (\(7/66\), 10.6%) tumors, and the mean tumor volume was 43.1 (\(\pm\)37.9) cm\({}^{3}\) (Table 2). Overall, a qualitative observation confirmed that the same pattern of projecting tractography that was observed in the smaller pilot cohort was also seen more generally in the larger cohort. The mean tract length was 29.1 (\(\pm\)11.7) mm, and the mean projecting tract length was 64.2 (\(\pm\)19.6). On average, each tractography demonstrated 5 (\(\pm\)2.1) distinct tract bundles projecting outward from the tumor ROI, with some of these corresponding to specific white matter pathways of known anatomic and functional importance (as shown in Table 2). Univariate linear regression analyses demonstrated statistically significant positive associations of MD and AD intra-tumoral dwMRI metrics with longer overall survival measured in days (\(\beta=504.75\)[28.20, 981.29], \(p=0.038\); \(\beta=474.17\)[30.69, 917.65], \(p=0.037\)). Stratifying the population according to several binary categorical variables, significant negative associations with survival were noted for tumors involving the corpus callosum (\(p<0.001\)), left-sided tumors (\(p=0.029\)), and tumors involving the inferior longitudinal fasciculus and/or inferior frontal-occipital fasciculus (\(p=0.008\)). While significant associations \begin{table}
\begin{tabular}{c c} \hline \hline
**Patient Characteristics (\(n=7\))** & \(n\) **(\%)/Mean (\(\pm\)SD)** \\ \hline \multicolumn{2}{c}{Clinical Outcomes} \\ Mortality at Last Follow-up & \(7\) (100\%) \\ Progression-Free (Days) & \(141.0\) (\(\pm\)94) \\ Overall Survival (Days) & \(308.5\) (\(\pm\)182.3) \\ \hline \multicolumn{2}{c}{Tumor Location and Structural Features} \\ Location, Frontal & \(1\) (14.3\%) \\ Location, Temporal & \(3\) (42.8\%) \\ Location, Parietal & \(3\) (42.8\%) \\ Location, Occipital & \(0\) \\ Location, Corpus Callosum & \(0\) \\ Location, Basal Ganglia/Thalamus & \(0\) \\ Laterality, Left & \(5\) (71.4\%) \\ Tumor Volume (cm\({}^{3}\)) & \(18.7\) (\(\pm\)4.2) \\ Number of Tumor Foci at Diagnosis & \(2.1\) (\(\pm\)2.2) \\ Multifocal at Diagnosis & \(3\) (42.9\%) \\ \hline \multicolumn{2}{c}{Generalized Q-Space Imaging (QSI)-Derived Tractography Features} \\ Mean Tract Length (mm) & \(23.2\) (\(\pm\)3.1) \\ Mean Projecting Tract Length (mm) & \(38.9\) (\(\pm\)4.9) \\ \hline \hline \end{tabular}
\end{table} 
Table 1: _Cont._between overall survival and tractography-related metrics including mean tract length, mean projecting tract length, and number of projecting tract bundles were not observed on the linear regression analysis, Kaplan-Meier survival statistics comparing the cohort stratified by quartile demonstrated significant negative effects on the overall survival of older age (\(p\) = 0.013), longer mean total tract length (\(p\) = 0.039), and longer mean projecting tract length (\(p\) = 0.022). Full Kaplan-Meier analyses including curves for these comparisons as well as stratification by tumor volume, MD, and number of projecting tract bundles observed are depicted in Figure 3.  
Figure 1: Tumor-associated tractography patterns in glioblastoma identified using QSI. Demonstration of tumor segmentation and visualization of tumor-associated projecting tractography derived from generalized q-space imaging (QSI, 3T, 64 gradient directions, b = 1000 s/mm\({}^{2}\)). Panels (**A–D**) demonstrate the workflow for manually segmenting the tumor regions of interest (ROI) using T2-weighted MRI registered with QSI (**B**). Colors represent the orientation of the vector: blue denotes superior–inferior directionality, red denotes left–right directionality, and green denotes anterior–posterior directionality.