O6-methyl-guanine-DNA methyltransferase methylation in serum and tumor DNA predicts response to 1,3-bis(2-chloroethyl)-1-nitrosourea but not to temozolamide plus cisplatin in glioblastoma multiforme.

Purpose: In glioblastoma multiforme (GBM), the cytotoxic effect of 1,3-bis(2-chloroethyl)-1-nitrosourea (BCNU) and temozolamide is dependent on O(6) alkylation, which correlates inversely with expression of the DNA repair enzyme O(6)-methyl-guanine-DNA methyltransferase (MGMT). Thus, MGMT assessment can be useful in predicting response in GBM, but the scarcity of neoplastic cells limits the practicality of MGMT assessment in these tumors. Although GBM grows within the skull, we investigated the concordance of methylation in glioma tissue, and paired serum DNA and the potential correlation with response and time to progression.