Impact of Extent of Resection for Gliomas

Mini Review

Austin J Surg. 2014;1(7): 1035.

Impact of Extent of Resection for Gliomas

Robert Bailey1 and Timothy H Lucas1,2*

1Department of Neurosurgery, University of Pennsylvania, USA

2Center for Neuroengineering & Therapeutics, University of Pennsylvania, USA

*Corresponding author: Timothy Lucas, Department of Neurosurgery, Translational Neuromodulation Lab, Center for Neuroengineering & Therapeutics, 3400 Spruce Street, 3rd Floor Silverstein, Philadelphia, PA 19104, USA

Received: September 03, 2014; Accepted: September 25, 2014; Published: October 07, 2014


Glioma; Extent of resection; Brain mapping; Overall survival


Brain tumors exact significant physical, emotional and economic burdens on patients, providers and the nation. In an era of personalized medicine and targeted therapeutics, surgical intervention remains pivotal in glioma management.

The goals of glioma surgery are to obtain a tissue diagnosis, reduce mass effect and achieve cytoreduction. Tissue diagnostics encompass pathological grading and comprehensive genetic profiling to target personalized therapeutics. Within the closed intracranial compartment, the rapid growth of a neoplasm causes mass effect and increased intracranial pressure. Decompression of space-occupying tumors lessens mass effect. Finally, cytoreduction lowers the burden of neoplastic clones that must be targeted with subsequent radiotherapy and chemotherapy.

Surgical success is ultimately defined by patient survival. A number of metrics are independent predictors of survival. Extent of Resection (EOR) is one such metric. In this overview, we review EOR in the context of the two common neoplastic conditions faced by neurosurgeons: Low Grade Glioma (LGG) and High Grade Glioma (HGG). These conditions differ greatly in treatment and prognosis, so we consider each individually. We begin by considering perioperative factors important for both conditions.

Perioperative Considerations

Treatment in the field of surgical oncology usually begins with wide surgical excision of the lesion to ensure clear tumor margins and lymph nodes free of disease. Glioma surgery is distinguished by the unique property of these lesions to infiltrate functional brain regions. Neurological deficits resulting from attempted resection of eloquent areas reduce quality of life, delay adjuvant therapy and hasten demise [1]. Consequently, Gross Total Resection (GTR) is not planned in cases where eloquent brain regions are invaded. Planning glioma surgery must balance maximal safe resection with the risk of inducing neurological deficits in a highly constrained physical environment.

Further, it is generally accepted that neoplastic cells infiltrate beyond the limits of the visible and radiographic boundaries of the lesion. A radiographic ’gross total resection’ more accurately describes a 99% volumetric cytoreduction. The remaining 1% represents diffuse microscopic residual disease that is too small to visualize radiographically with intravenous contrast agents. Surgical planning therefore anticipates the need for adjuvant therapy to the surgical margins and the possibility of local recurrence.

Planning glioma surgery requires specialized radiography and techniques. Specifically, the preoperative workup includes structural Magnetic Resonance Imaging (MRI), Functional MRI (fMRI), magnetic resonance spectroscopy and Diffusion Tensor Imaging (DTI) (Figure 1A, B, C). If the lesion is near speech areas, direct stimulation of the brain during surgery may be necessary. These modalities are used to develop a surgical trajectory clear of eloquent cortical regions and the white matter tracts that link them. The most fundamental requirement is the structural MRI. Isotropic voxels of T1-weighted sequences are acquired in gapless slices to create a 3-dimentional volume that is registered to the patient’s superficial landmarks with optical imaging in the operating room to build a model of the brain during surgery. This affords the surgeon a real-time anatomical navigation tool that can ’see’ through bone, dura and brain to visualize deep lesions. So enabled, the glioma surgeon may strategize an approach to optimize the resection while minimizing iatrogenic deficits. This technique has been transformative in modern neurosurgery and is the backdrop against which we consider the evidence for extent of resection.

Citation: Bailey R and Lucas TH. Impact of Extent of Resection for Gliomas. Austin J Surg. 2014;1(7): 1035. ISSN: 2381-9030.