Researchers from the Mayo Clinic have reported that patients with glioblastoma who are receiving enzyme-inducing anticonvulsant (EIAC) drugs may have improved outcomes compared with similar patients with glioblastoma not taking such drugs. The details of this study appeared in the October 13, 2009 issue of Neurology.[1]

Glioblastoma is one of the most common and fatal types of primary brain cancer. Patients with glioblastoma typically have a poor prognosis, and treatment is usually palliative. The standard initial treatment is surgery followed by radiation therapy and chemotherapy. The median survival is approximately one year, and the three-year survival is less than 10%. Patients with a good performance status who have undergone surgery have an improved survival. Studies have shown that radiotherapy and chemotherapy improve survival regardless of other adverse risk factors. Second-line therapies are not often effective.

The current study was prompted by concern that EIAC anticonvulsants could induce hepatic P 450 microsomal enzymes and accelerate the metabolism of chemotherapeutic or targeted agents used to treat glioblastoma.  They evaluated anticonvulsant therapy in 650 patients with Glioblastoma. Seventy-two percent were receiving EIAC drugs, 2% were receiving non-EIAC anticonvulsants, and 26% were not receiving anticonvulsants. Overall survival was 12.3 months for EIAC users compared with 10.7 months for non-users. Progression-free survival was 5.6 months for EIAC users and 4.8 months for non-users. These authors stated: “Paradoxically, enzyme-inducing anticonvulsant (EIAC) use correlated with superior outcome of patients with glioblastoma. These results suggest that in comparative clinical trials testing agents metabolized by P450 microsomal enzymes, treatment arms may need stratification for the proportion of patients receiving EIAC.”

Comments: These are interesting findings, which may lead to new insights into the treatment of patients with glioblastoma.

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