C11 Methionine PET (MET-PET) Imaging of Glioblastoma for Detecting Post-operative Residual Disease and Response to Chemoradiation Therapy

Publication date: Available online 18 June 2018
Source:International Journal of Radiation Oncology*Biology*Physics
Author(s): Yingbing Wang, Otto Rapalino, Pedram Heidari, Jay Loeffler, Helen A. Shih, Kevin Oh, Umar Mahmood
Purpose/ObjectivesResponse criteria of glioblastoma after chemoradiation do not account for metabolic changes that occur after treatment. The purpose of this study is to evaluate the utility of positron emission tomography imaging with C11 Methionine (MET-PET) for detecting changes that occur after chemoradiation therapy and the value of molecular biomarkers for predicting magnitude of metabolic response.Materials and MethodsNewly diagnosed glioblastoma patients undergoing standard chemoradiation treatment were enrolled in this prospective imaging study with MET-PET scan performed within 3 days following surgical resection and again at 4 weeks after completion of chemoradiation. Near contemporaneous contrast enhanced MRI (ceMRI) was performed within 2 weeks of each MET-PET. MET-PET imaging was analyzed for SUVmax, SUVmean, and SUVvolume on a multimodality workstation (Syngovia 24B, Siemens).ResultsA total of 18 subjects underwent baseline post-operative MET-PET imaging, of which 14 subjects underwent post-chemoradiation MET-PET imaging. Among subjects who showed residual MET-avid disease on immediate post-operative MET-PET scans and also underwent post-chemo radiation MET-PET imaging (n=10), mean ΔSUVmax was -40% (range -100%-0%), mean ΔSUVmean was -35% (range -100%-0%), and mean ΔSUV volume was -64% (range -100%-0%). Δtumor/brain reference was -40% (range -100%-0%) using SUVmax and -35% (range -100%-0%) using SUVmean. In contrast, none of the T2 weighted images on ceMRI showed reduction in abnormal T2/FLAIR signal by greater than 25% by visual assessment. ΔSUVmax, ΔSUVmean, and ΔSUVvolume correlated with MGMT methylation status (p=0.01), but not with EGFR, or c-MET amplification status. All patients were IDH-1 wildtype.ConclusionsMET-PET scanning shows significant decrease in metabolic signal at 1 month post-chemoradiation compared to the immediate post-operative period, even when T2/FLAIR changed little. MGMT promoter methylation status further predicts differential metabolic responses. MET-PET may be a useful tool for delineation of radiation targets and assessment of response.

Teaser

C11 Methionine PET may be a useful tool for delineation of radiation targets and assessment of response in glioblastoma. C11 Methionine PET scanning can show a significant decrease in extent of MET-avid glioblastoma at 1 month after completion of chemoradiation compared to the immediate post-operative period, even when T2/FLAIR changes little. MGMT promoter methylation status further predicts differential metabolic responses.


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