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Oligodendroglioma – 1p/19q Co-Deletion — SCE Neurology MCQ

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ModerateNeuro-oncologyOligodendroglioma – 1p/19q Co-DeletionSCE Neurology

A 55-year-old woman is diagnosed with an oligodendroglioma, WHO grade 3, following biopsy of a left frontal lobe lesion. Molecular testing shows 1p/19q co-deletion and IDH1 R132H mutation. What is the prognostic significance of 1p/19q co-deletion?

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Correct answer: A — It indicates a better prognosis and predicts response to PCV chemotherapy

1p/19q co-deletion is a defining molecular feature of oligodendrogliomas (WHO 2021 classification). It is associated with a significantly better prognosis compared to astrocytomas of the same grade and predicts a favourable response to PCV (procarbazine, lomustine, vincristine) chemotherapy. The CODEL and RTOG 9402 trials confirmed survival benefit from PCV in 1p/19q co-deleted tumours. IDH mutation further improves prognosis. A: The opposite — it confers a better prognosis. C: GBMs are IDH-wildtype without 1p/19q co-deletion. D: It is a strong prognostic and predictive marker. E: It is a primary brain tumour marker.

Reference: WHO CNS Tumour Classification (2021); NICE NG99 Brain Tumours (2021)