CHICAGO―Adding bevacizumab to standard first-line chemoradiotherapy does not improve survival rates among patients with newly-diagnosed glioblastoma, reported authors of a phase 3 double-blind, placebo-controlled multi-institutional clinical trial presented at the 2013 American Society of Clinical Oncology (ASCO) Annual Meeting.

Bevacizumab was also associated with higher rates of side effects compared to chemoradiotherapy, reported Mark R. Gilbert, MD, of the M. D. Anderson Cancer Center in Houston, TX, and coauthors.

“First line bevacizumab did not improve overall survival (OS) for patients with glioblastoma,” Dr. Gilbert said. “Progression-free survival (PFS) was longer, but did not reach a study-specified target (p value).”

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A total of 637 patients who had undergone surgery for newly-diagnosed glioblastoma were randomly assigned to receive temozolomide plus radiation or placebo or chemoradiation plus bevacizumab. 

Median OS was 16.1 months for patients receiving placebo and 15.7 months among patients receiving bevacizumab, a nonsignificant statistical  difference (P=0.21).

Median PFS was longer for patients receiving bevacizumab than placebo (10.7 vs. 7.3 months; P=0.007), but the difference failed to reach a predetermined threshold for statistical significance. Nor were MGMT methylation status or gene expression signatures associated with improved survival among patients receiving bevacizumab, Dr. Gilbert reported.

Bevacizumab was associated with “significant worsening of neurocognitive function over time compared to placebo,” noted Dr. Gilbert. Quality-of-life data also showed an overall decline among patients receiving bevacizumab, he said.

The implications for the role of bevacizumab in glioblastoma treatment need to be clarified in light of the study, according to CNS tumors expert Howard Fine, MD.

Bevacizumab, a vascular endothelial growth factor A inhibitor, is an intuitively promising treatment for glioblastoma, a malignancy for which angiogenesis is “one of the most prominent features,” Dr. Gilbert noted. Most patients with glioblastoma are administered bevacizumab at some point in their treatment, he said.