Retrospective analysis of glioblastoma patients treated with bevacizumab who presented with multifocal disease at diagnosis.

Abstract

2080 Background: Glioblastoma patients who present with multifocal disease have an extremely poor prognosis – a recent analysis at our institution demonstrated a median survival of 6 months, versus 11 months for a cohort of unifocal glioblastoma patients matched for age, extent of resection, and KPS. Bevacizumab is frequently used to treat patients with recurrent or progressive glioblastoma. However, its benefit in the setting of multifocal disease is unproven, particularly in light of the concern that antiangiogenic treatment may promote a more invasive, multifocal, and potentially treatment-resistant phenotype. Methods: Between 2004 to 2010, 368 patients were diagnosed with glioblastoma at our institution. We identified 46 patients with multifocal disease on initial presentation, and retrospectively reviewed their clinical course and treatment history. Kaplan-Meier estimates and Wilcoxon tests were used to assess survival distribution. Results: Of the 46 patients with multifocal disease, 12 were treated with bevacizumab (7 upfront and 5 at first recurrence). All 12 bevacizumab-treated patients received external beam radiation therapy, and 11 received temozolomide. In the bevacizumab-treated cohort, median age at the time of surgery was 59 years, and median KPS was 80. For the 34 patients with multifocal disease who did not receive bevacizumab, median age was 69 years, and median KPS was 75. Median survival for the bevacizumab-treated patients was 12.9 months, with 12-month survival of 58.3%. By comparison, median survival for patients with multifocal disease who did not receive bevacizumab was 5.8 months, with 12-month survival of 20.6%. The difference in survival between the two groups was statistically significant, with p-value of 0.045 by the Wilcoxon test. Conclusions: This single-institution retrospective analysis suggests that bevacizumab treatment is associated with a survival benefit for glioblastoma patients who present with multifocal disease. One can infer that the clinical benefit of bevacizumab in this setting outweighs any potential concerns regarding the ability of bevacizumab to promote an invasive, treatment-resistant tumor phenotype.