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MO_13_2506 - Radiation-induced White Matter Injury Following Radiation Therapy in Glioblastoma patients

Monday, October 22
10:45 AM - 12:15 PM
Location: Innovation Hub, Exhibit Hall 3

Radiation-induced White Matter Injury Following Radiation Therapy in Glioblastoma patients
H. Elhalawani1, T. Li2, S. Radwan2, K. A. Al Feghali3, Y. Ding4, A. S. Mohamed3, C. D. Fuller5, H. Zhu3, and C. Chung6; 1Department of Radiation Oncology, University of Texas MD Anderson Cancer Center, Houston, TX, 2MD Anderson Cancer Center, Houston, TX, 3The University of Texas MD Anderson Cancer Center, Houston, TX, 4The University of Texas MD Anderson Cancer Center, Department of Radiation Physics, Houston, TX, 5University of Texas Graduate School of Biomedical Sciences, Houston, TX, 6Princess Margaret Hospital, Toronto, ON, Canada

Purpose/Objective(s): The use of high-dose radiation therapy (RT) in glioblastoma multiforme (GBM) patients is limited by radiation-induced brain injury. We aim at studying and comparing the patterns of acute and early-delayed white matter injury adjacent to tumor tissue after RT using diffusion tensor imaging (DTI). The different patterns of white matter structural changes at different phases can provide clinicians with a better understanding of the neuropathological consequences of therapeutic RT.

Materials/Methods: Eligible patients were ≥18 years old and treated with surgery and concurrent chemoradiation (CRT) for GBM between 2007-2013, and also had serial acquisitions of conventional MRI and DTI. Clinical and demographic information was recorded for eligible patients. DTI data were analyzed at the following time points: prior to RT after tumor resection (Pre-RT), 1 month after RT (1-mo post-RT), and 6 months after RT (6-mo post-RT). MR imaging data sets for each patient, including DTI and T1-weighted, were co-registered across all time points as well as with the planning CT (encompassing the planning target volumes, 3D dose grid and RT plan). The planning volumes included the gross tumor volume (GTV) and clinical target volume (CTV). Fractional anisotropy (FA) changes between the pre-RT and the 2 post-RT DTI imaging sets were calculated using the histogram of the FA changes through a log-hazard transformation of the estimated kernel density. Demographic and tumor predictors of FA change were evaluated using linear regression.

Results: A total of 38 eligible patients (24 males; 12 females) with mean age of 55.8 (range 26.5-72.5) were evaluated. There was a significant decrease in the log-hazard functions of the FA change within the CTV/GTV volumes between pre-RT and both 1-mo post-RT (p=0.01) and 6-mo post-RT (p=0.0001). In the acute phase (1-mo post-RT), a significantly greater decrease in FA was seen in younger patients (<55 years old) (p=0.016) and subtotal resection/gross total resection (as compared to biopsy) (p=0.048). There was a trend to suggest different FA responses based on tumor location with a non-significant increase in FA in the temporal lobe (p=0.09) at 1-mo post-RT and a significant decrease in FA in the frontal lobe at 6-mo post-RT (p= 0.002) compared to pre-RT.

Conclusion: This retrospective study identified early significant changes in FA on DTI at 1 month and 6 months following chemoradiation in adult patients with newly diagnosed GBM. Younger patients (<55 years) and frontal location of the tumor seem to be associated with more pronounced decreases in FA. This early radiation-related white matter reaction may suggest a process such as demyelination. Further prospective investigation in conjunction with more detailed clinical evaluation is needed.

Author Disclosure: H. Elhalawani: Employee; MD Anderson Cancer Center. T. Li: None. S. Radwan: None. K.A. Al Feghali: None. Y. Ding: None. A.S. Mohamed: None. C.D. Fuller: Research Grant; National Institutes of Health, National Science Foundation, Elekta AB. Grant funding; Elekta AB. Honoraria; Nederlandse Organisatie voor Wetenschappelijk Onde. Consultant; Elekta AB, Nederlandse Organisatie voor Wetenschappelijk Onde. Travel Expenses; Elekta AB, Nederlandse Organisatie voor Wetenschappelijk Onde. Reviewer; Radiological Society of North America. Associate Editor; Radiographics. Data Management Task Force Committee Member; MR-LinAc Consortium. Member; National Cancer Institute. Task Group Member; American Association of Physicists in Medicine. H. Zhu: None. C. Chung: None.

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