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Radionecrosis — SCE Medical Oncology MCQ

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HardCNS TumoursRadionecrosisSCE Medical Oncology

A 58-year-old man develops a brain lesion 18 months after completing stereotactic radiosurgery for a single brain metastasis from lung cancer. MRI shows an enhancing lesion at the previous SRS site. How can radionecrosis be distinguished from tumour recurrence?

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Correct answer: E — MRI perfusion (rCBV), MR spectroscopy and FDG-PET or amino acid PET (e.g. FET-PET) help differentiate — radionecrosis typically shows low perfusion and low metabolism

Differentiating radionecrosis from tumour recurrence after SRS is a common diagnostic challenge. Advanced MRI techniques (dynamic susceptibility contrast perfusion showing low rCBV in necrosis, MR spectroscopy showing high lipid/lactate ratio) and metabolic PET imaging (FDG-PET or amino acid PET such as FET/MET showing low uptake in necrosis) are the key discriminating tools. If diagnosis remains uncertain, stereotactic biopsy may be required. Bevacizumab has demonstrated efficacy in symptomatic radionecrosis.

Reference: NICE NG99 Brain tumours; ESMO 2024 Brain Metastases Guidelines; Vellayappan et al Neuro-Oncol 2018