Glioblastoma Resection


Maximizing Surgical Resection of Glioblastomas—the Intraoperative MRI

by John Park, MD, PhD, neurosurgeon

 

Gliomas are the most common primary tumors of the brain. They arise from the neoplastic transformation of neural stem cells or of glial cells such as astrocytes or oligodendrocytes.

 

Histological criteria defined by the World Health Organization (WHO) are used to grade the relative malignancy of gliomas along a progressive four-point scale. “Pilocytic astrocytomas,” which generally occur in children, are considered grade I or benign and complete surgical resection is the treatment of choice as it is often curative.

John Park, MD

 


The most common grade II tumors are “low-grade astrocytomas” and “oligodendrogliomas.” While these tumors are also considered benign, they can progress over time to higher grades. Complete surgical resection, if possible, is the treatment of choice for grade II tumors as well. Grade III tumors are considered malignant and the most common examples are “anaplastic astrocytomas” and “anaplastic oligodendrogliomas.” Surgical resection followed by adjuvant radiation therapy and chemo- therapy is recommended. The most common and malignant glioma is the “glioblastoma multiforme” (a.k.a. “glioblastoma” or “GBM”). Glioblastomas are classified as grade IV tumors.1

 

The initial treatment for a brain lesion suspected of being a glioblastoma on a magnetic resonance imaging study is a surgical procedure such as a biopsy, a partial resection or a gross total resection to establish a histologic diagnosis. Following confirmation that the lesion is a GBM, the current standard of care is the concurrent administration of radiation therapy and temozolomide chemotherapy followed by the administration of temozolomide alone. A randomized, controlled trial comparing radiation alone to the combination of radiation and chemotherapy demonstrated the superiority of the latter.2

 

In contrast, there is a lack of consensus on the best initial surgical management of patients, in part due to the absence of a prospective trial demonstrating the efficacy of one procedure over the others. Several retrospective studies have, however, shown a clear association between greater extent of tumor resection and increased survival as well as more favorable response to chemotherapy. One of the initial studies to show this found that patients who had more than or equal to 98 percent of their tumors resected survived longer than those who had less than 98% removed. Subsequent studies have confirmed these results and have shown that removal of even more than 78 percent is beneficial to patients.3

 


Pre-operative T1-weighted contrast enhanced axial MRI image shows a heterogeneously enhancing mass in the left frontal lobe that is suspicious for a malignant primary brain tumor.

 

A first intraoperative T1-weighted contrast enhanced axial MRI image shows a central resection cavity surrounded by a rim of enhancing tumor tissue. Shadows in the front and back of the head are due to artifacts caused by the surgical head-holder. A second intraoperative T1-weighted contrast enhanced axial MRI image shows gross total resection of the enhancing tumor tissue.


 

Among the tumor characteristics leading to partial rather than gross total resection are proximity to eloquent brain regions, diffuse or multifocal nature, deep white matter location and large size. Tumors located directly in motor, speech, or visual areas generally cannot be completely resected without exacerbating existing neurological deficits or inducing new ones. Tumors located in close proximity to such functionally important areas may, however, be gross totally resectable with the aid of sophisticated intraoperative monitoring techniques such as cortical and subcortical motor mapping, productive and receptive speech testing, and visual evoked potential analysis. Another predisposing factor to the partial resection of a GBM is the lack of a distinct tumor- brain interface. Although the appearance and texture of frank tumor tissue significantly differs from that normal brain tis- sue, it is sometimes difficult to determine where one transitions into the other. The use of intraoperative MRI scanning allows the surgeon to periodically monitor the extent of tumor resection to ensure that a maximal amount of tumor tissue is removed prior to the completion of the operation and the transport of the patient out of the operating room. The following case illustrates the use of the intraoperative MRI to achieve a gross total resection of a glioblastoma in the left frontal lobe. Mr. G. is an otherwise healthy 55-year- old male without any significant previous medical history. Over the past few weeks, he had been having intermittent headaches, which were relieved with acetaminophen. On the day of presentation, he was riding his bicycle when he developed uncontrollable twitching of his right hand and inability to speak. The episode was witnessed by his wife and lasted approximately 10 minutes in total.

 

His wife brought him to the emergency room where an evaluation was performed. He denied any headaches, speech difficulties or weakness. His review of systems was negative, and he reported no recent travel out of the area. His general medical examination was within normal limits and on neurological testing, his mental status, cranial nerves, motor, sensory, cerebellar and reflex examinations were all non-focal. An MRI of the brain revealed a lesion in the left frontal lobe that heterogeneously enhanced with gadolinium contrast on T1-weighted imaging and that was hyperintense to brain on T2-weighted imaging. The lesion was suspicious for a primary brain tumor and a gross total resection was recommended given its location in the left frontal lobe. After an understanding the risks and benefits, the patient consented to surgery in the intraoperative MRI suite.

 

The patient was brought into the intraoperative MRI suite and general anesthesia was induced. He underwent a left frontal craniotomy with initial use of a standard intraoperative image guidance system. All grossly abnormal tissue was resected and hemostasis was achieved within the resection cavity. An intraoperative MRI scan was performed which revealed residual enhancing tumor tissue around the periphery of the resection cavity. Using this new intraoperative MRI scan as a guide, additional tumor tissue was resected.

 

A second intraoperative MRI scan was performed which revealed that the tumor had now been gross totally resected. The dura was closed, the craniotomy bone flapped was secured in place, and the galea and scalp were closed. The patient was awakened from general anesthesia, extubated, and taken to the intensive care unit. The patient was discharged to home on post-operative three without any complications. Histologic analysis of the tumor indicated that it was a glioblastoma and the patient subsequently underwent outpatient radiation and temozolomide chemotherapy.

 

To meet the specialists at Santa Barbara Neuroscience Institute at Cottage Health System, visit www.sbni.org. To refer a patient, please contact the transfer center at 1-888-MY-CAL-NEURO.

 

 


 

References:

1. Louis DN, Ohgaki H, Wiestler OD, et al. The 2007 WHO classification of tumours of the central nervous system. Acta Neuropathol 2007;114:97-109.

2. Stupp R, Mason WP, van den Bent MJ, et al. Radiotherapy plus concomitant and adjuvant temozolomide for glioblastoma. N Engl J Med 2005;352:987-96.

3. Eyupoglu IY, Buchfelder M, Savaskan NE. Surgical resection of malignant gliomas—role in optimizing patient outcome. Nat Rev Neurol 2013;9:141-51.


 

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