Abstract
Background
Based on the positive results of our pilot study that evaluated MR diffusion tensor imaging characteristics in the white matter of 13 subjects with glioblastoma, we aimed to evaluate the prognostic value of diffusion restriction in a new, larger cohort of glioblastoma patients.
Material and Methods
Thirty-five subjects diagnosed with glioblastoma were treated by surgical resection, radiotherapy, temozolomide and TTFields (Optune®). All subjects were followed by MRI at 1.5 T approximately every two months (total range 160–1810 days) with standard imaging, including diffusion-weighted imaging, until tumor progression. Apparent diffusion coefficient (ADC) maps were calculated using FSL and freehand ROIs were placed on B0 images within the T2 hyperintense white matter (T2HWM) near the resection cavity by a single investigor (AMR), and then projected onto the ADC maps. Additionally, an ROI was similarily placed within the normal-appearing white matter (NAWM). Final values (ADC-ratio) were calculated by dividing ADC in T2HWM by ADC in NAWM. Linear regression slopes (ADC-ratio vs. time) for individual subjects were fitted in R.
Results
In 26 subjects a positive slope was observed in ADC-ratio over time, while in the remaining subjects the slope was negative. We found a significant difference between subjects with positive and negative regression slopes in overall survival (OS; hazard ratio = 0.27 [0.1–0.69], log rank p = 0.009) and progression-free survival (PFS; harazd ratio = 0.31 [0.12–0.81], log rank p = 0.02), with positive regression slope associated with more favorable outcome.
Conclusion
Our data suggest that increasing ADC in the affected (T2 hyperintense) white matter of glioblastoma patients is favorable, with significantly greater PFS and OS in patients with increasing ADC over time. Changes in ACD likely reflect changes in tumor density in the afftected white matter, with decreasing values (increasing diffusion restriction) corresponding to tumor progression.