Intensity modulated radiation therapy versus three dimensional
conformal radiation therapy for treatment of high grade glioma: A
radiobiological modeling study
Affiliations: University of Oklahoma Health Sciences Center,
Oklahoma City, OK, USA | British Columbia Cancer Agency, Victoria, Canada
Note: [] Corresponding author: Salahuddin Ahmad, Ph.D., University of
Oklahoma Health Sciences Center, Department of Radiation Oncology, 825 N.E.
10{th}, Suite 1430, Oklahoma City, Oklahoma, OK 73104, USA. Tel.: +1 405 271
5641; Fax: +1 405 271 8297; E-mail: salahuddin-ahmad@ouhsc.edu
Abstract: Treatment of glioblastoma results in a median survival of 12 months.
Radiation dose escalation trials for high grade gliomas have resulted in modest
improvements in survival in selected patients with small peripheral tumors at
the expense of normal brain toxicity. Neurotoxicity includes radiation necrosis
but it is increasingly recognized that long-term survivors may develop
neuro-cognitive deficits. Tumor control probability (TCP) and normal tissue
complication probability (NTCP) are radiobiological models used to predict
treatment outcomes. This study assesses the impact of radiation dose escalation
from 59.6 Gy to 90 Gy on TCP and NTCP in ten patients planned with Three
Dimensional Conformal Therapy (3DCRT) and Intensity Modulated Radiation Therapy
(IMRT). No difference in TCP was observed between 3DCRT and IMRT at doses of
59.4 Gy and 90 Gy. However, dose escalation to 90 Gy resulted in about 25%
relative TCP increase. Compared to 3DCRT, dose escalation with IMRT
significantly reduced NTCP by 70% (10.75% v. 3.75%, respectively). As a result,
highly conformal techniques are recommended to obviate radiation exposure of
normal brain especially when radiation dose escalation is used. Further
understanding of the molecular mechanisms underlying neurotoxicity will allow
the development of more precise radiobiological predictive models and of
approaches to prevent or treat radiation-induced brain damage.
Keywords: High grade glioma, dose escalation, radiobiological modeling
