The prognostic value of maximal surgical resection is attenuated in oligodendroglioma subgroups of adult diffuse glioma: a multicenter retrospective study.

Purpose: Maximal surgical resection is associated with survival benefit in the majority of studies in adult diffuse glioma. This study aims to characterize the prognostic value of surgical resection in molecular subgroups of diffuse glioma.

Methods: 1178 patients with diffuse glioma from our centers and 422 from TCGA dataset were collected. The Kaplan-Meier analysis and multivariable Cox regression models were conducted to identify the prognostic value of surgical resection through different histological and molecular stratifications.

Results: Firstly, we confirmed progression-free survival (PFS) benefit associated with gross total resection (GTR) over sub-total resection (STR) in lower-grade glioma (HR 1.49; 95% CI 1.17-1.90; P = 0.001). Intriguingly however, we were unable to detect a significant PFS or overall survival (OS) benefit in oligodendroglioma (N = 397; HR 1.36; 95% CI 0.86-2.14; P = 0.19 and HR 1.05; 95% CI 0.55-1.99; P = 0.89, respectively). Secondly, when analyzed in molecular subgroups, we were similarly unable to detect a significant PFS or OS benefit in IDH MT/codel subgroup (N = 269; HR 1.47; 95% CI 0.92-2.34; P = 0.11 and HR 1.54; 95% CI 0.78-3.05; P = 0.21, respectively), oligodendroglioma with IDH MT/codel subgroup (N = 233; HR 1.33; 95% CI 0.79-2.21; P = 0.28 and HR 1.16; 95% CI 0.53-2.54; P = 0.70, respectively) or other relevant subgroups. TCGA validation also showed a significant survival benefit in astrocytoma rather than oligodendroglioma. Exploratory RNAseq analysis displayed that fewer cell proliferation-related gene expression features were specific to oligodendroglioma.

Conclusion: These results suggest that the benefit of maximal surgery may be attenuated in patients within oligodendroglioma relevant subgroups because of the chemosensitive and indolent nature. The aggressive surgery accompanying with risk of neurologic morbidity may be unnecessary for these patients given the lack of survival benefit with gross total resection.