TSPO imaging in glioblastoma multiforme: A direct comparison between 123ICLINDE-SPECT, 18F-FET PET and gadolinium-enhanced MRI.

Here we compare TSPO imaging using 123 I-CLINDE and amino acid transport imaging using 18 F-FET and investigate if 123 I-CLINDE is superior to 18 F-FET in predictingprogression of glioblastoma multiforme (GBM) at follow up.

Methods  Three patients with WHO grade IV GBM were scanned with 123 I-CLINDE SPECT, 18 F-FET PET and Gadolinium enhanced magnetic resonance imaging (gadolinium-MRI). Molecular imaging data were compared to follow-up gadolinium-MRI or contrast enhanced computed tomography (CE-CT).

Results  The percentage overlap between volumes of interest (VOIs) of increased 18 F-FET uptake and 123 I-CLINDE binding was variable (12-42%). The percentage overlap of gadolinium-MRI baseline VOIs was greater for 18 F-FET (79-93%) than 123 I-CLINDE (15-30%). Contrary, VOIs of increased contrast enhancement at follow-up compared to baseline overlapped to a greater extent with baseline 123 I-CLINDE VOIs than 18 F-FET VOIs (21% vs. 8 % and 72% vs. 55%).

Conclusion  Our preliminary results suggest that TSPO brain imaging in GBM could be a useful tool for predicting tumor progression at follow up and less susceptible to changes in blood-brain barrier (BBB) permeability than 18 F-FET. Larger studies are warranted to test the clinical potential of TSPO imaging in GBM including pre-surgical planning and radiotherapy.