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  • The Impact of Extent of Resection on IDH1 Wild-Type or Mutant Low-Grade Gliomas

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    Toral R Patel MD; Evan D Bander MD; Rachael A Venn; Tiffany L Powell Avila MD; Gustav Y Cederquist; Peter M Schaefer; Luis A Puchi; Akbarshakh Akhmerov; Shahiba Ogilvie MPH; Anne Reiner; Nelson Moussazadeh MD; Viviane S. Tabar MD

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    Meeting: Congress of Neurological Surgeons 2017 Annual Meeting

    Introduction: Accumulating evidence suggests that maximizing extent of resection (EOR) improves outcomes for patients with WHO grade II low-grade gliomas (LGG). However, recent studies demonstrate that LGGs bearing a mutation in the isocitrate dehydrogenase 1 (IDH1) gene are a distinct molecular and clinical entity. It remains unclear whether maximizing EOR confers an equivalent clinical benefit in IDH mutated (mtIDH) and IDH wild-type (wtIDH) LGGs. To answer this question, we evaluated a cohort of patients with surgically-resection WHO grade II gliomas and known IDH1 mutation status, to assess the impact of EOR on malignant progression-free survival (MPFS) and overall survival (OS).

    Methods: We performed a retrospective review of 74 patients with WHO grade II gliomas and known IDH mutational status undergoing surgical resection at a single institution. EOR was assessed with quantitative three-dimensional volumetric analysis. The effect of predictor variables on MPFS and OS was analyzed with Cox regression models and the Kaplan-Meier method.

    Results: 52 (70%) mtIDH patients and 22 (30%) wtIDH patients were included. Median pre-operative tumor volume was 37.4 cm3 (range: 0.9-190.2 cm3). Median EOR was 57.6% (range: 0.08% – 99.3%). Median follow-up was 44.4 months. Malignant progression was identified in 31 patients and 17 patients died. Univariate Cox regression analysis confirmed EOR as a prognostic factor for the entire cohort. However, Cox regression analysis stratified by IDH status demonstrated that a greater EOR independently prolonged MPFS and OS for wtIDH patients (HR = 0.002 [95% CI 0.000 - 0.074] and HR = 0.001 [95% CI 0.00 - 0.108], respectively), but not for mtIDH patients (HR = 0.84 [95% CI 0.17 - 4.13] and HR = 2.99 [95% CI 0.15 - 61.66], respectively).

    Conclusions: Increasing EOR confers oncologic and survival benefits in IDH1 wild-type LGGs. However, the impact of EOR on IDH1 mutant LGGs is less significant and requires further study.

    Patient Care: This study expands our existing knowledge base regarding the optimal surgical management of low-grade gliomas. It is anticipated that the data presented here will impact surgical decision making in this patient population.

    Learning Objectives: By the conclusion of this session, participants should be able to: 1) Understand the prognostic implications of an IDH mutation in low-grade gliomas 2) Describe the role of surgery for low-grade gliomas 3) Discuss the nuances in surgical management of IDH mutated vs. IDH wild-type LGGs


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