But biopsies are invasive procedures that come with risks.
“Complications, such as bleeding or infarction — the obstruction of blood supply — could aggravate a patient’s existing neurological status,” says Dr. Thanh Nguyen, a neuroradiologist at The Ottawa Hospital and an associate professor at the University of Ottawa’s Faculty of Medicine. “Some patients have a tumour in a very sensitive area — in the brain stem or the thalamus, for example — where it might not be safe to do a biopsy.”
This has motivated Dr. Nguyen to seek out an alternative, non-invasive method of improving the diagnosis of gliomas and predicting the patient’s prognosis. He is currently investigating whether an imaging technique called MR spectroscopy can act as a “virtual biopsy”.
Brain tumours produce certain metabolites, which doctors can use to determine the type of glioma in question. Some gliomas grow slowly and are considered relatively benign, while other types are malignant and grow rapidly. Doctors use the presence or absence of specific metabolites in a patient’s tumour to determine whether or not it is dangerous.
For example, the MR technique that Dr. Nguyen is examining allows him to find and quantify a specific biomarker called 2-Hydroxyglutarate. Patients who have this metabolite in their tumour generally have a better chance of survival than those who don’t.
“In the past, brain imaging techniques were not powerful enough to pick up on certain metabolites because they are present in the brain at very small concentrations,” says Dr. Nguyen. “MRI machines are more powerful now, so we have the option of looking into these metabolites preoperatively.”
And if that’s the case, we might be able to avoid a biopsy in patients who have tumours in sensitive areas of the brain.
“That's where the Metabolomics Core Facility comes in. For the last two years, we have been collecting tissue samples from brain surgeries. We intend to send biopsy samples from 100 patients to the core facility so that their team can analyze the metabolites from these samples.”
“Core facilities make expensive experimental equipment available to a large number of researchers, so they help facilitate new discoveries and innovations, and they help promote good research practices,” says Shama Naz, the Metabolomics Core Facility manager. “Our facility provides access to high-throughput mass spectrometry instruments and expert personnel to help investigators better understand the roles of metabolites in basic, translational and clinical research.”
For this particular project, the core facility will identify and quantify the different molecules that are present in the tumour samples so that Dr. Nguyen can compare the readings with his own MR spectroscopy findings. The goal is to find out whether both methods reach similar conclusions about the contents of the tumours.
“If the findings are similar enough, we might be able to rely on imaging to guide treatment rather than perform biopsies when it is unsafe,” says Dr. Nguyen. “Finding a prognostic tool that is non-invasive might reduce the risk of harm to patients. That’s why I’m passionate about this project and it’s what motivates me to do my best.”