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GBM Recurrence vs Radiation Necrosis – Advanced Imaging — SCE Neurology MCQ

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HardNeuro-oncologyGBM Recurrence vs Radiation Necrosis – Advanced ImagingSCE Neurology

A 60-year-old man with a WHO grade 4 glioblastoma treated with the Stupp protocol develops progressive neurological deterioration 4 months after completing chemoradiotherapy. MRI brain shows an enlarging enhancing lesion at the resection margin. His neuro-oncologist considers whether this represents true tumour progression or radiation necrosis. What investigation may help differentiate?

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Correct answer: D — MR perfusion or FDG-PET/amino acid PET — high perfusion/high metabolism suggests tumour recurrence; low perfusion/low metabolism suggests radiation necrosis

Differentiating true tumour recurrence from radiation necrosis (which can appear identical on conventional MRI) is a major clinical challenge. Advanced imaging modalities can help: MR perfusion (rCBV) — tumour recurrence typically shows elevated rCBV (increased vascularity) whereas radiation necrosis shows low rCBV. FDG-PET or amino acid PET (e.g. 18F-FET PET) — tumour recurrence shows increased metabolic activity. However, definitive diagnosis may still require biopsy. A: CT is less informative than MRI. C: LP is not routinely helpful. D: No reliable serum tumour markers for GBM. E: Genetic testing does not differentiate recurrence from necrosis.

Reference: NICE NG99; RANO Criteria; EAN Glioma Guidelines