Dynamics of hypercellular glioma regions identified with diffusion-weighted imaging for adaptive radiotherapy on an MR-Linac
Liam S. P. Lawrence1,2, Rachel W. Chan1, James Stewart3, Mark Ruschin3, Aimee Theriault3, Sten Myrehaug3, Jay Detsky3, Pejman J. Maralani4, Chia-Lin Tseng3, Greg J. Stanisz1,2,5, Arjun Sahgal3, and Angus Z. Lau1,2
1Physical Sciences Platform, Sunnybrook Research Institute, Toronto, ON, Canada, 2Department of Medical Biophysics, University of Toronto, Toronto, ON, Canada, 3Department of Radiation Oncology, Sunnybrook Health Sciences Centre, Toronto, ON, Canada, 4Department of Medical Imaging, Sunnybrook Health Sciences Centre, Toronto, ON, Canada, 5Department of Neurosurgery and Paediatric Neurosurgery, Medical University, Lublin, Poland
For radiotherapy of high-grade glioma, dose escalation to hypercellular tumour could improve local control, but changes during treatment might necessitate target volume adaptation. Since hypercellular tumour causes low apparent diffusion coefficient (ADC) values, volumetric changes in low-ADC regions were quantified using near-daily MR-Linac imaging to evaluate adaptation necessity. Low-ADC regions increased in volume (median extremal change: 12.2%) and changed rapidly for certain patients (maximum growth/shrinkage rate: 7.1/9.1% per day). Low-ADC regions changed more in magnitude and grew more rapidly for resected tumours than intact ones. These findings imply that adaptation may be required for dose escalation to hypercellular glioma regions.
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