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September 10, 2025Open Access

Prognosis of Idh-Mutant Adult Low-Grade Glioma in the Modern Era

Key Points

RT+CT improved progression-free survival compared to RT-alone in IDH-mutant LGG patients.
Patients with oligodendrogliomas in Group 2 had a longer progression-free survival than those in Group 1.
More complete resections occurred in Group 2, suggesting advancements in surgical approaches.
No significant changes were observed in seizure occurrence between the two treatment groups.

Abstract

Abstract AIMS Since 2016, the standard oncological treatment of high-risk adult diffuse IDH-mutant low-grade gliomas (LGG) after initial surgery has changed from the sole use of radiotherapy (RT-alone) to the combined use of radio- therapy and chemotherapy (RT+CT). This study aimed to determine the uptake and effectiveness of RT+CT in a real-world environment by comparing survival and seizure outcomes in two cohorts treated in a single centre, pre- and post-2016. METHODS Retrospective collection of adult patient data diagnosed with IDH-mutant LGG treated at University College London Hospitals from 2009-2015 (Group 1) and 2016-2022 (Group 2). The Progression-Free Survival (PFS), Overall Survival (OS), and seizure outcomes of the two cohorts were analysed. RESULTS 78 patients were treated in Group 1 and 79 in Group 2. There were more Complete Resections in Group 2 com- pared with Group 1 (53% vs 19%). As expected, more patients were treated with RT+CT in Group 2 than Group 1 (25% vs 10%) and vice versa for RT-alone (45% vs 10%). RT+CT led to a signiﬁcant increase in PFS (3.2 vs 7 years, p=0.02) but not OS compared with RT-alone. PFS was longer in Group 2 patients with oligodendrogliomas (but not astrocytomas) compared with Group 1 (median not reached vs 6.4 years), with the survival curves diverg- ing at 3 years. PFS was signiﬁcantly greater in the RT+CT patients who had Biopsy-only compared with those who had Partial/Complete Resections. No signiﬁcant differences were found in seizure occurrence/frequency between the two groups. CONCLUSION RT+CT improved PFS but not OS or seizure outcomes in patients with IDH-mutant oligodendrogliomas and pa- tients who had Biopsy-only. Given the long natural history of these tumours, it has not yet been possible to demonstrate improvements in OS. Patients with astrocytomas who had Partial/Complete Resections could be potentially spared from the additional CT noting the adverse effects and insigniﬁcant survival beneﬁts.

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