The role of extent of resection in IDH1 wild-type or mutant low-grade gliomas

BACKGROUND: Maximizing extent of resection (EOR) improves outcomes in adults withWorld Health Organization (WHO) grade II low-grade gliomas (LGG). However, recentstudies demonstrate that LGGs bearing a mutation in the isocitrate dehydrogenase 1 (IDH1)gene are a distinct molecular and clinical entity. It remains unclear whether maximizingEOR confers an equivalent clinical beneft in IDH mutated (mtIDH) and IDH wild-type(wtIDH) LGGs.OBJECTIVE: To assess the impact of EOR on malignant progression-free survival (MPFS)and overall survival (OS) in mtIDH and wtIDH LGGs.METHODS: We performed a retrospective review of 74 patients with WHO grade II gliomasand known IDH mutational status undergoing resection at a single institution. EOR wasassessed with quantitative 3-dimensional volumetric analysis. The effect of predictorvariables on MPFS and OS was analyzed with Cox regression models and the Kaplan-Meiermethod.RESULTS: Fifty-two (70%) mtIDH patients and 22 (30%) wtIDH patients were included.Median preoperative tumor volume was 37.4 cm3; median EOR of 57.6% was achieved.Univariate Cox regression analysis confrmed EOR as a prognostic factor for the entirecohort. However, stratifying by IDH status demonstrates that greater EOR independentlyprolonged MPFS and OS for wtIDH patients (hazard ratio [HR] = 0.002 [95% confdenceinterval {CI} 0.000-0.074] and HR = 0.001 [95% CI 0.00-0.108], respectively), but not for mtIDHpatients (HR = 0.84 [95% CI 0.17-4.13] and HR = 2.99 [95% CI 0.15-61.66], respectively).CONCLUSION: Increasing EOR confers oncologic and survival benefts in IDH1 wtLGGs, butthe impact on IDH1 mtLGGs requires further study.