The IDH paradox: Meta-analysis of alkylating chemotherapy in IDH-wildtype and -mutant lower grade gliomas

IDH-wildtype (-wt) status is a pre-requisite for the diagnosis of glioblastoma (GBM); however, IDH-wt gliomas with low grade or anaplastic morphology have historically been excluded from GBM trials and may represent a distinct prognostic entity. While alkylating agent chemotherapy improves overall s...

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Published inNeuro-oncology (Charlottesville, Va.)
Main Authors Kinslow, Connor J, Roy, Soumyajit, Iwamoto, Fabio M, Brown, Paul D, DeStephano, David M, Canoll, Peter D, Qureshi, Summer S, Gallito, Matthew, Sisti, Michael B, Bruce, Jeffrey N, Horowitz, David P, Kachnic, Lisa A, Neugut, Alfred I, Yu, James B, Mehta, Minesh P, Cheng, Simon K, Wang, Tony J C
Format Journal Article
LanguageEnglish
Published England 29.06.2024
Subjects
isocitrate-dehydrogenase
meta-analysis
radiotherapy
glioma
alkylating chemotherapy
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Summary:IDH-wildtype (-wt) status is a pre-requisite for the diagnosis of glioblastoma (GBM); however, IDH-wt gliomas with low grade or anaplastic morphology have historically been excluded from GBM trials and may represent a distinct prognostic entity. While alkylating agent chemotherapy improves overall survival (OS) and progression-free survival (PFS) for IDH-wt GBM and also IDH-mutant gliomas, irrespective of grade, the benefit for IDH-wt diffuse histologic lower grade gliomas is unclear. We performed a meta-analysis of randomized clinical trials for World Health Organization (WHO) grade 2-3 gliomas (2009 to present) to determine the effect of alkylating chemotherapy on IDH-wt and -mutant gliomas using a random-effects model with inverse-variance pooling. We identified six trials with 1,204 patients (430 IDH-wt, 774 IDH-mutant) that evaluated alkylating chemoradiotherapy versus radiotherapy alone, allowing us to perform an analysis focused on the value of adding alkylating chemotherapy to radiotherapy. For patients with IDH-wt tumors, alkylating chemotherapy added to radiotherapy was associated with improved PFS (HR:0.77 [95%CI 0.62-0.97], P=.03) but not OS (HR:0.87 [95%CI 0.64-1.18], P=.17). For patients with IDH-mutant tumors, alkylating chemotherapy added to radiotherapy improved both OS (HR:0.52 [95%CI 0.42-0.64], P<.001) and PFS (HR=0.47 [95%CI 0.39-0.57], P<.001) compared to radiotherapy alone. The magnitude of benefit was similar for IDH-mutant gliomas with or without 1p19q-codeletion. Alkylating chemotherapy reduces mortality by 48% and progression by 53% for patients with IDH-mutant gliomas. Optimal management of IDH-wt diffuse histologic lower grade gliomas remains to be determined, as there is little evidence supporting an OS benefit from alkylating chemotherapy.
ISSN:1523-5866