Recent studies have shown that
isocitrate dehydrogenase 1/2 (IDH1/2) mutations occur frequently in secondary
glioblastoma. This study aimed to investigate their impact on
temozolomide chemosensitivity and relationship with
O(6)-methylguanine DNA methyltransferase (MGMT) promoter methylation in secondary
glioblastoma. Searches for IDH1 and IDH2 mutations, 1p19q codeletion, MGMT promoter methylation, and p53 expression were carried out in a series of 86 secondary
glioblastomas and correlated with progression-free survival and overall survival. Response to
temozolomide was evaluated by progression-free survival, as well as by
tumor size on successive MRI scans, then correlated with molecular alterations. IDH (IDH1 or IDH2) mutations were found in 58/79 patients (73.4%). IDH mutation, MGMT promoter methylation, and 1p19q codeletion were associated with prolonged progression-free survival in univariate (P < 0.001, P < 0.001, P = 0.003, respectively) and multivariate analysis (P < 0.001, P < 0.001, P = 0.035, respectively). IDH mutation (P = 0.001) and MGMT promoter methylation (P = 0.011) were correlated with a higher rate of objective response to
temozolomide. Further analysis of response to
temozolomide showed that patients with both IDH mutation and MGMT promoter methylation had the best response rate to
temozolomide. IDH mutation appears to be a significant marker of positive chemosensitivity in secondary
glioblastoma. Use of IDH status combined with MGMT promoter status as a stratification factor seems appropriate in future clinical trials involving
temozolomide for the treatment of patients with secondary
glioblastoma.