Comparative Analysis of Methods for Detecting Isocitrate Dehydrogenase 1 and 2 Mutations and Their Metabolic Consequence, 2-Hydroxyglutarate, in Different Neoplasms.

Isocitrate dehydrogenase (IDH) mutations have been recognized in a few neoplasms including glioma, acute myeloid leukemia, chondrosarcoma, cholangiocarcinoma, and angioimmunoblastic T-cell lymphoma. The direct methods to detect IDH mutations include DNA sequencing, immunohistochemistry (IHC), or by measuring its byproduct, 2-hydroxyglutarate (2-HG), in the blood or urine. Moreover, conventional magnetic resonance imaging can be modified to magnetic resonance spectroscopy (MRS) to measure 2-HG in tumor. By conducting a search in Medline/PubMed and ISI/Web of Science for the published articles in English related to the methods for detection of IDH mutations and its byproduct 2-HG, we compared different methodologies to detect these mutations and discuss advantages and limitations of each method. Studies in which a methodology of detection was compared with another modality were included. Multiple studies have shown that both DNA sequencing and IHC are reliable methods for detecting IDH mutations in glioma and other solid neoplasms. IHC appeared to be less costly, easier to perform, and may be slightly more accurate than DNA sequencing. 2-HG has also been measured in bone marrow aspirate, serum and urine of patients with mutant IDH acute myeloid leukemia, and correlated very well with sequencing and IHC. Lastly, in some glioma patients, MRS detected IDH mutations noninvasively and reliably with excellent correlations with other modalities such as IHC and sequencing. In conclusion, IHC, MRS, and 2-HG detection all are clinically useful and comparable with DNA sequencing in identifying IDH mutations in different neoplasms. 2-HG and MRS can be utilized for monitoring treatment response in a variety of neoplasms.