Researchers analyze relationship between extent of resection and outcome in patients with glioblastoma

May 7 2010

Gliomas arise from the supporting cells of the brain, called the glia. These cells are subdivided into astrocytes, ependymal cells and oligodendroglial cells (or oligos). These tumors are graded from the lowest grade 1 to highest grade 4, with glioblastoma multiforme (GBM) being the highest grade and deadliest type of glioma. About 50 percent of all gliomas diagnosed annually are high-grade.

High-grade glioma or GBM is the most common primary malignant brain tumor, as well as the most devastating, accounting for 19 percent of all primary brain tumors. Standard treatment includes surgical resection followed by chemotherapy and radiation therapy. Unfortunately, despite decades of refinement, this multimodal approach still translates to a mean survival of only 12 to 14 months.

Researchers at the Barrow Neurological Institute in Phoenix and the University of California, San Francisco, analyzed the relationship between extent of resection and patient outcome in 500 patients with glioblastoma. The results of this study, The Value of Glioblastoma Extent of Resection: A Volumetric Analysis of 500 Patients, will be presented by Nader Sanai, MD, 11:55 am to 12:09 pm, Wednesday, May 5, 2010, during the 78th Annual Meeting of the American Association of Neurological Surgeons in Philadelphia. Co-authors are Zaman Mirzadeh, MD, PhD, Mei-Yin Polley, PhD, and Mitchel S. Berger, MD, FACS. Dr. Sanai will be presented with the National Brain Tumor Foundation Mahaley Award for this research.

In the last decade, mounting evidence suggests that greater surgical extent of resection is associated with longer glioblastoma patient survival. "While this data has helped establish a fragile and frequently debated consensus that glioblastoma resection improves patient outcome, the impracticality of conducting a randomized clinical trial limits any ability to quantify the value of greater tumor resection," stated Dr. Sanai.

Beyond establishing a diagnosis and decompressing tumor mass effect, the value of surgical resection of glioblastomas remains controversial. To date, only one study has rigorously quantified the survival benefit of microsurgical resection in glioblastoma patients. This work suggested that a 98 percent extent of resection or greater was necessary to significantly improve survival. In the modern era, this report serves as a critical study of reference for the neurosurgical community, justifying an "all-or-none" approach commonly practiced in the surgical management of glioblastoma.

The reported findings represent the most comprehensively-studied glioblastoma patient population to date. The findings analyzed outcome in 500 consecutive, newly diagnosed supratentorial glioblastoma patients treated at UCSF from 1992-2009. Clinical, radiographic, and outcome parameters were measured for each patient, including volumetric tumor analysis using T-1 weighted contrast-enhanced MRI.

•Median age of patient group: 60.0 years
•Median Karnofsky performance status (KPS): 80
•Mean tumor volume prior to surgery: 65.8 cm3
•Mean tumor volume post surgery: 2.3 cm3
•Many tumors (346) occupied eloquent brain areas
•All patients underwent resection followed by radiation and chemotherapy
•Mean clinical follow-up: 12.8 months
•Survival rates: 0.4 months to 64.2 months

"The findings demonstrated that an extent of resection > 78 percent can improve patient survival, with this association continuing even at the highest levels of resection," remarked Dr. Sanai. "The study strongly suggests that greater extent of resection for newly-diagnosed patients should be of critical concern to the neurosurgical oncologist, even when a gross-total resection is not possible," concluded Dr. Sanai.

SOURCE American Association of Neurological Surgeons