IDH-1(R132H) mutation status in diffuse glioma patients: implications for classification

WHO(2007) grading of diffuse gliomas in adults is well-established. However, IDH mutations make classification of gliomas according to the WHO(2007) edition controversial. Here, we characterized IDH-1(R132H mut) status in a cohort of 670 adult patients with different WHO(2007) grades of diffuse glioma. Patient characteristics, clinical data and prognoses were obtained from medical records. Patients with IDH-1(R132H mut) were younger and had better clinical outcomes than those without mutations. Differences in age among patients with astrocytomas of different WHO(2007) grades were eliminated after patients were grouped based on IDH-1(R132H) status. IDH-1(R132H mut) was present more often in patients with lower Ki-67 and MGMT protein levels and higher mutant p53 levels. Ki-67 was also strongly associated with WHO(2007) grade independently of IDH-1(R132H mut) status. Moreover, patients with Ki-67<30 survived longer than those with Ki-67≥30, regardless of IDH-1(R132H mut) status. Patients in the IDH-1(R132H mut) group with lower MGMT protein levels also had better clinical outcomes than those in other groups. Our results indicate that to better treat gliomas, IDH mutation status should be included when determining WHO(2007) grade in glioma patients.