An extent of resection threshold for newly diagnosed glioblastomas

Clinical article

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Object

The value of extent of resection (EOR) in improving survival in patients with glioblastoma multiforme (GBM) remains controversial. Specifically, it is unclear what proportion of contrast-enhancing tumor must be resected for a survival advantage and how much survival improves beyond this threshold. The authors attempt to define these values for the patient with newly diagnosed GBM in the modern neurosurgical era.

Methods

The authors identified 500 consecutive newly diagnosed patients with supratentorial GBM treated at the University of California, San Francisco between 1997 and 2009. Clinical, radiographic, and outcome parameters were measured for each case, including MR imaging–based volumetric tumor analysis.

Results

The patients had a median age of 60 years and presented with a median Karnofsky Performance Scale (KPS) score of 80. The mean clinical follow-up period was 15.3 months, and no patient was unaccounted for. All patients underwent resection followed by chemotherapy and radiation therapy. The median postoperative tumor volume was 2.3 cm3, equating to a 96% EOR. The median overall survival was 12.2 months. Using Cox proportional hazards analysis, age, KPS score, and EOR were predictive of survival (p < 0.0001). A significant survival advantage was seen with as little as 78% EOR, and stepwise improvement in survival was evident even in the 95%–100% EOR range. A recursive partitioning analysis validated these findings and provided additional risk stratification parameters related to age, EOR, and tumor burden.

Conclusions

For patients with newly diagnosed GBMs, aggressive EOR equates to improvement in overall survival, even at the highest levels of resection. Interestingly, subtotal resections as low as 78% also correspond to a survival benefit.

Abbreviations used in this paper: EOR = extent of resection; GBM = glioblastoma multiforme; KPS = Karnofsky Performance Scale; RPA = recursive partitioning analysis; 5-ALA = 5-aminolevulinic acid.

Article Information

Current affiliation for Dr. Sanai: Barrow Neurological Institute, Phoenix, Arizona.

Address correspondence to: Mitchel S. Berger, M.D., Department of Neurological Surgery, University of California at San Francisco, 505 Parnassus Avenue, M779, San Francisco, California 94143. email: bergerm@neurosurg.ucsf.edu.

Please include this information when citing this paper: published online March 18, 2011; DOI: 10.3171/2011.2.JNS10998.

© AANS, except where prohibited by US copyright law.

Headings

Figures

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    Kaplan-Meier survival curve for all 500 newly diagnosed patients with GBM, demonstrating a median overall survival of 12.2 months. Numbers on the y axis represent percent survival throughout.

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    Select Kaplan-Meier survival curves for 100%, 90%, 80%, and 78% EOR thresholds. Corresponding overall survival times beyond each threshold value were 16, 13.8, 12.8, and 12.5 months, respectively.

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    Overlay of survival curves for total, subtotal, and partial resections.

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    Stepwise improvement in overall survival when comparing 90%, 95%, 98%, and 100% EOR thresholds.

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    The RPA results identify each of the following: patient age, KPS score, EOR, and tumor volume as predictive of overall survival (OS) (p < 0.0001). Four distinct risk groups are each predictive of outcome.

  • View in gallery

    Kaplan-Meier survival curves for each RPA stratification group demonstrate a stepwise improvement in overall survival.

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