Malignant gliomas represent the majority of primary brain tumors in adults and are among the most intractable tumors. Cancers reprogram their metabolism to meet the needs of rapid cell growth. Alterations in metabolite abundance may serve as biomarkers of malignancy, and the capability to monitor the changes non-invasively would have significant clinical utility in cancer. Gliomas often contain a specific metabolic activty that is predictive of the genotype and has predictive value with respect to tumor stage and patient survival. A high fraction of gliomas contain mutations in the metabolic enzymes, isocitrate dehydrogenase (IDH) 1 and 2. These heterozygous mutations are confined to the active site of the enzyme and result in a neomorphic activity that causes the mutant enzyme to produce an "oncometabolite", 2-hydroxyglutarate (2HG). Non-invasive identification of this onco-metabolite by MRS is therefore a major breakthrough in cancer research. Beyond simple detection of 2HG, our preliminary data show that 2HG is a remarkably sensitive biomarker for monitoring tumor progression and response to treatment in IDH mutated gliomas. Glycine (Gly) is a biomarker of tumor malignancy, as indicated in prior studies. Our data also indicate that citrate (Cit) is elevated in gliomas. Over the course of this preliminary study, there has been crucial need for 3D evaluation of these onco-metabolites within the tumor mass. Here, we propose to examine the clinical utility of 2HG, Gly and Cit, in a large cohort of subjects using multi-slice 2D MRSI at 3T. In order to accomplish this goal, we have assembled a multi-disciplinary work team of MR scientist, neuro-oncologist, neurologist, radiologist and biostatistician, who will contribute their expertise in the fields.
The specific aims i nclude, firs, an in-vivo MRS study for the disease specificity of 2HG (Aim 1). We will examine clinically proven non-glioma lesions who mimic glioma in clinical MRI. To increase the clinical applicability of the result, we will select non-enhancing brain diseases, given that IDH mutation occurs largely in grade-2 and -3 gliomas, which are often non-enhancing. Second, we will examine the clinical utility of 2HG, Gly, Cit and other metabolites in patients with IDH mutated gliomas (Aim 2). Third, we will examine the clinical utility of Gly, Cit and other metabolites in patients with IDH wild type gliomas (Aim 3).
In Aim 2 and 3, the patients will undergo MRSI scans at multiple time points, and we will monitor the metabolic changes with tumor progression and in response to treatment. We anticipate our study will provide significant value in many aspects of management of gliomas. 3D evaluation of the cancer biomarkers using MRSI will provide biological insights for making the diagnosis of gliomas, tracking of infiltrative cells during follw up, and determining response to treatment. Success of the 2HG specificity study in non-glioma neurological diseases will provide an experimental evidence for use of non-invasive 2HG imaging as a triaging tool in the workup of a new brain mass.
The goal of this project is to examine the disease specificity of 2-hydroxyglutarate in non-glioma brain lesions, and the clinical utility of 2-hydroxyglutarate, glycine and citrate in IDH mutated gliomas and IDH wild type gliomas.