Introduction: Surgery is first line therapy for glioblastoma (GB) and there is evidence that gross total resection (GTR) is associated with improved survival. GTR, however, is not always possible and the relationship between percent resection (EOR) and survival is unclear. The goals of this study were to evaluate if there is an association between EOR and survival for all GB, eloquent GB, and GB capable of GTR. A better understanding of these associations may help to optimize surgical care for patients with GB.

Methods: Adult patients who underwent surgery of a newly diagnosed intracranial GB at an academic tertiary-care institution from 2007-2011 were retrospectively reviewed. Pre and postoperative volumes were measured in a semi-automated fashion using MRI with gadolinium obtained prior to and within 48 hours after surgery. Cox regression analysis was used to identify if an association existed between volumetric EOR and survival. Tumor location was assessed by three neurosurgeons blinded to patient outcomes.

Results: 292 patients met the inclusion criteria, where 128 involved eloquent (motor and/or language) cortex and 87 were capable of GTR. The median survival of all patients was 12.7 months, and the median[IQR] pre and postoperative tumor volumes were 29.5[13.1-54.3]cm3 and 2.8[0.1-10.5]cm3, respectively. For all GB, increasing EOR was independently associated with survival [HR(95%CI); 0.994(0.990-0.997), p=0.0008], and the minimum EOR survival threshold was >70%. For eloquent tumors, EOR was also independently associated with prolonged survival [HR(95%CI);0.406(0.240-0.700),p=0.001], and the minimum EOR was >65%. For patients where GTR could be achieved, EOR was independently associated with prolonged survival [HR(95%CI);0.972(0.958-0.986),p=0.006], and the minimum EOR was >95% (p=0.01).

Conclusions: Surgery for GB requires a fine balance between EOR and avoiding iatrogenic deficits. This study establishes thresholds necessary for prolonging survival for patients with GB, which differs between patients with and without eloquent tumors.

Patient Care: Surgery is first line therapy for glioblastoma (GB) and there is evidence that gross total resection (GTR) is associated with improved survival. GTR, however, is not always possible and the relationship between percent resection (EOR) and survival is unclear. The goals of this study were to evaluate if there is an association between EOR and survival for all GB, eloquent GB, and GB capable of GTR. A better understanding of these associations may help to optimize surgical care for patients with GB.

Learning Objectives: To identify if extent of resection is associated with prolonged survival for patients with glioblastoma, and if there is a resection threshold that is associated with improved outcomes

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