A 35-year-old presents with headaches and MRI shows a 3 cm WHO Grade 2 IDH-mutant, 1p/19q co-deleted oligodendroglioma in the left frontal lobe. He is neurologically intact. What is the current WHO 2021 classification and significance of 1p/19q co-deletion?
- A Astrocytoma, IDH-mutant, WHO Grade 2; 1p/19q status not prognostically relevant in astrocytomas
- B Glioblastoma, IDH-wildtype; requires urgent surgery and concurrent chemoradiation
- C Oligodendroglioma, IDH-mutant, 1p/19q co-deleted, WHO Grade 2; co-deletion predicts chemosensitivity to PCV and improved prognosis ✓
- D Ependymoma; complete surgical resection is curative in 70% of cases
Explanation
Per WHO 2021 CNS tumor classification, IDH-mutant gliomas with 1p/19q co-deletion are classified as oligodendroglioma (Grade 2 or 3), a distinct entity from IDH-mutant astrocytoma (which retains 1p/19q). The 1p/19q co-deletion results from a translocation t(1;19) and is a favorable prognostic and predictive marker: it predicts response to alkylating chemotherapy (PCV — procarbazine, CCNU, vincristine — or temozolomide) and is associated with longer overall survival. The RTOG 9402 and EORTC 26951 trials established that adding PCV chemotherapy to RT improves OS in co-deleted oligodendrogliomas, including a survival benefit of approximately 10 years in Grade 2 tumors.
Reference: Bailey & Love's Short Practice of Surgery, 27th ed.
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