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Abstract Details

Longitudinal Volumetric Analysis of FLAIR Hyperintensity Following Radiation Therapy (RT) in Patients with Low-grade Glioma (LGG)
P4 - Poster Session 4 (11:45 AM-12:45 PM)
With radiation and chemotherapy, patients with IDH-mutant LGG can achieve many years of survival. RT may induce long-term changes within and adjacent to the radiation field, complicating the distinction between post-radiation treatment effects and advancing tumor. Better understanding of volumetric post-radiation FLAIR changes will help with clinical interpretation of disease progression vs treatment effect and guide management decisions.

To characterize the changes in MRI FLAIR hyperintensity that occur in LGG patients following RT, to better understand the “pseudoprogression” that occurs in absence of true tumor regrowth.

In this IRB-approved retrospective study, serial MRI scans of patients with LGG were reviewed, including pre-RT and for 2.5 years post-RT. Segmentation for volumetric analysis was performed with manual supervision using ITK-SNAP (open-source segmentation software). Descriptive statistics are reported.

Sixteen patients with histologic grade 2 gliomas were included (4 astrocytoma, 12 oligodendroglioma, 15/16 confirmed IDH mutation).  Time from histologic diagnosis to RT ranged from 2.2 to 235 months (median 6.9 months). 159 MRI scans were segmented using ITK-SNAP (median 9.5 MRIs/patient, range 4-13). Mean pre-RT tumor volume was 31.6 cm3 (std dev 29, range 5-100 cm3). Nine of 16 MRIs showed decreasing FLAIR volume immediately post-RT, while 7/16 showed increasing FLAIR volume.  After the initial post-RT MRI, 12/16 patients had MRIs with an increase in FLAIR volume sometime during the first year (pseudoprogression).  The FLAIR volume stabilized or decreased a median of 18.4 months and mean of 15.0 months post-RT. During the 2.5 year study period, median progression free survival and median overall survival were not reached (14/16 patients alive, 12/16 progression free). 

FLAIR hyperintensity changes on MRI are highly variable in the first 1.5 years post-RT in low grade glioma, but after 1.5 years, FLAIR volumes stabilize and decrease, likely indicating the inflection point where post-RT pseudoprogression stabilizes.

Isabella Sutherland
Ms. Sutherland has nothing to disclose.
Adam Ulano No disclosure on file
Alissa A. Thomas, MD, FAAN (University of Vermont Medical Center) Dr. Thomas has received personal compensation in the range of $5,000-$9,999 for serving as a Consultant for Roon. The institution of Dr. Thomas has received research support from Novocure. The institution of Dr. Thomas has received research support from Ono Pharmaceuticals.