GBM – Pseudoprogression — SCE Neurology MCQ

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ModerateNeuro-oncologyGBM – PseudoprogressionSCE Neurology

A 70-year-old woman with glioblastoma multiforme treated with the Stupp protocol presents 3 months after completing chemoradiotherapy with a new enhancing lesion adjacent to the resection cavity. A follow-up MRI 6 weeks later shows the lesion has spontaneously decreased in size without further treatment. What is the most likely explanation?

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Correct answer: C — Pseudoprogression

Pseudoprogression is a treatment-related phenomenon occurring in 20–30% of GBM patients within the first 3 months after concurrent temozolomide and radiotherapy. It results from an inflammatory response to treatment-induced tumour cell death, causing a transient increase in contrast enhancement that mimics tumour progression. It spontaneously resolves without additional treatment and is associated with MGMT promoter methylation (which predicts better treatment response). It is distinguished from true progression by interval decrease on follow-up imaging. A: True recurrence would continue to grow. C: Radiation necrosis typically occurs later (>6 months post-RT). D: No infection history. E: Haemorrhage would show different signal characteristics.

Reference: NICE NG99 Brain Tumours (2021); RANO Criteria (2010)