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Review
. 2016 Dec 18:13:386-394.
doi: 10.1016/j.nicl.2016.12.020. eCollection 2017.

The use of amino acid PET and conventional MRI for monitoring of brain tumor therapy

Affiliations
Review

The use of amino acid PET and conventional MRI for monitoring of brain tumor therapy

Norbert Galldiks et al. Neuroimage Clin. .

Abstract

Routine diagnostics and treatment monitoring of brain tumors is usually based on contrast-enhanced MRI. However, the capacity of conventional MRI to differentiate tumor tissue from posttherapeutic effects following neurosurgical resection, chemoradiation, alkylating chemotherapy, radiosurgery, and/or immunotherapy may be limited. Metabolic imaging using PET can provide relevant additional information on tumor metabolism, which allows for more accurate diagnostics especially in clinically equivocal situations. This review article focuses predominantly on the amino acid PET tracers 11C-methyl-l-methionine (MET), O-(2-[18F]fluoroethyl)-l-tyrosine (FET) and 3,4-dihydroxy-6-[18F]-fluoro-l-phenylalanine (FDOPA) and summarizes investigations regarding monitoring of brain tumor therapy.

Keywords: Bevacizumab; Checkpoint inhibitors; FDOPA; FET; Glioma; Immunotherapy; MET; PET; Pseudoprogression; Pseudoresponse; Temozolomide.

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Figures

Fig. 1
Fig. 1
Patient with a newly diagnosed glioblastoma. After resection and chemoradiation with temozolomide, MR and FET PET images show residual tumor in the left frontal lobe (baseline imaging for radiotherapy planning) with complete metabolic response 10 weeks after radiotherapy. The residual contrast-enhancing lesion is metabolically inactive (arrows) indicating a post-treatment effect. This is confirmed 22 months later with complete resolution of this lesion.
Fig. 2
Fig. 2
A 67-year old glioblastoma patient prior to adjuvant chemotherapy (images on the left). After two cycles of temozolomide chemotherapy (images on the right), a clear decrease of both the metabolically active tumor volume and tumor/brain ratios can be observed whereas conventional MRI shows no change of contrast enhancement (“stable disease” according to RANO criteria).
Fig. 3
Fig. 3
A 52-year-old patient with a progressive anaplastic oligoastrocytoma according to the WHO classification 2007 (top row). During follow-up after 8 and 12 months (middle and bottom row) of biweekly bevacizumab therapy, MRI shows a markedly reduction of contrast enhancement and T2 hyperintensity. Correspondingly, FET PET shows a decrease of metabolic activity by means of maximum tumor/brain ratio reduction (TBRmax).

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