By optimizing an imaging technique, the edited magnetic resonance spectroscopy, Institut du Cerveau – ICM researchers managed to detect very precisely a certain type of brain tumors non-invasively. A key step for diagnosis, prognosis and treatment of patients with glioma.
40% of gliomas, the most frequent brain tumor, have a mutation in the IDH gene. This mutation is associated with an intracellular accumulation of a molecule called 2HG. The detection of 2HG levels makes possible to diagnose those tumors and is of major interest for patient care. Is the tumor a glioma or not? Does it have the specific IDH gene mutation? This information will have several consequences, on surgery, treatment, and prognosis of the patient.
Until recently, the detection of IDH mutation and 2HG accumulation could only be quantified by analyzing tumor biopsies, an invasive procedure. Recent studies have shown that it is possible to detect this molecule non-invasively with magnetic resonance spectroscopy (MRS).
Several methods can be used with this imaging technique but the specificity and the sensitivity can be unsatisfying. A high specificity and sensitivity are needed to avoid getting false positive results.
In the present study, the researchers managed to optimize the acquisition technique and the post processing methods of MRS. They tested it on 24 subjects with suspected diagnosis of low grade glioma and compared it with the most commonly used method nowadays.
“Our method shows better results than those currently used in other research centers worldwide. We demonstrate a specificity and a sensitivity for detecting the 2HG metabolite of 100%.“ Francesca Branzoli, research engineer at Institut du Cerveau – ICM
The researchers now want to use their method for the follow-up of patients who undergo radiotherapy or chemotherapy, to monitor their reaction to therapies. This technique could also be used to follow the effect of new drugs in clinical trials, in particular new drugs in development which target specifically the 2HG oncometabolite.
“Overall the edited MRS represents one of the most reliable tool to predict IDH mutation. In clinical practice it could be highly beneficial for noninvasive diagnosis of gliomas, prognosis determination and patients’ follow-up.” Marc Sanson, neuro-oncologist and team leader at Institut du Cerveau – ICM.
Did you know: Magnetic resonance spectroscopy (MRS)
Magnetic resonance spectroscopy is an imaging technique which allows to measure the concentration of several metabolites in the body.
It is based on the principle that different metabolites have specific chemical properties and molecular composition which can be detected noninvasively with MRS. Thus, each metabolite is characterized by its own magnetic signal. An MRS recording consists of a spectrum composed of several peaks, each corresponding to a different metabolite.
This technique can be used in clinic as the concentration of metabolites may vary in different diseases. For example neuronal dysfunction or atrophy in neurodegenerative diseases can be measured through the altered concentration of specific metabolites present specifically in neurons.
Référence : Highly specific determination of IDH status using edited in vivo magnetic resonance spectroscopy. Branzoli F, Di Stefano AL, Capelle L, Ottolenghi C, Valabrègue R, Deelchand DK, Bielle F, Villa C, Baussart B, Lehéricy S, Sanson M, Marjanska M. Neuro Oncol. 2017 Nov 6.