Abstract B13: Growth kinetics in glioblastome multiforme: Response to radiation and the quantification of treatment response
Authors: Rayfield Corbin , Rockne Russ , Hawkins-Daruud Andrea , Jacobs Joshua , Swanson Kristin R. 
Published: May 2016

Abstract
High-grade gliomas, commonly known as glioblastoma multiforme (GBM), exhibit linear radial expansion. In untreated patients, these growth kinetics are believed to be constant. Not much is known about the changes in growth kinetics that different treatment regimes induce. In this study we sought to compare pre-treatment growth kinetics to post-treatment growth kinetics; investigate correlations between pre-, during, and post-treatment growth kinetics survival, and time-to-progression; and elucidate measures of response to treatment that define post-treatment growth characteristics.
Patient information and MRIs were obtained from 62 newly diagnosed patients with glioblastoma from Northwestern University, University of Washington, and University of California, Los Angeles who had at least 2 pre-treatment MRIs and 1 post-treatment MRI. The tumor growth kinetics were calculated by selecting 2 imaging events, separated by at least 5 days, and calculating the rate of growth according to:
Velocity=(T1Gdradius2-T1Gdradius1)/(t2-t1)
Velocities were compared with survival and time-to-progression using log-rank survival analysis in Prism 6.0 (Graphpad Software).
There was no significant correlation between pre-treatment velocity and overall survival or time-to-progression (n=50). The velocity during radiation treatment was correlated with overall survival. A growth rate of less than 9.125 mm/year during the course of radiation portended greater overall survival (p-value &lt; 0.001). To take into account the previous rate of growth, the pre-treatment velocity was compared to the growth rate during radiation. A relative change of greater than 110% (i.e. the tumor's growth was faster during the course of radiation) correlated with the time to recurrence (p-value= 0.016). The post-treatment velocity was correlated with overall survival. If the tumor grew at a rate greater than 2.87 mm/year after finishing radiation, the patient's survival was significantly less than those patients whose tumors grew at less than 2.87 mm/year.
Interestingly, the growth kinetics prior to treatment do not correlate with response metrics. Instead, the response to radiation stratifies patients into survival categories that allow providers to more accurately predict clinical progression. Rather than the current ‘wait-and-see’ scheme of clinical decision-making, metrics of GBM growth kinetics that are calculated off of standard-of-care MRIs could allow for implementation of salvage therapies and secondary options in patients with low treatment response.
Citation Format: Corbin Rayfield, Russ Rockne, Andrea Hawkins-Daruud, Joshua Jacobs, Kristin R. Swanson. Growth kinetics in glioblastome multiforme: Response to radiation and the quantification of treatment response. [abstract]. In: Proceedings of the AACR Special Conference: Advances in Brain Cancer Research; May 27-30, 2015; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2015;75(23 Suppl):Abstract nr B13.