Molecular Classification of Brain Tumors Could Lead to Targeted Therapies

The classification of brain tumors by their molecular characteristics will likely become the standard within the next year, a shift that is expected to lead to more accurate diagnoses and targeted therapies for people with gliomas – the most common form of brain tumor in adults.

“We’re finally reaching a point where we’re really going to have a molecular classification of brain tumors, which is something we’ve been trying to get to for a long time,” said Dr. Stephen Coons, chief of the Section of Neuropathology at Barrow Neurological Institute. Watch Dr. Coons’ talk.

At its spring 2016 meeting, the World Health Organization is expected to make molecular classification the new standard for diagnosing brain tumors and finalize the algorithm that will be used.

The current processBrain_Tumors_Graphic for classifying a brain tumor is to send a tumor sample to a neuropathologist, who looks at the sample underneath a microscope and classifies the tumor based on the microscopic appearance of the tumor.  Molecular testing is sometimes used to refine the classification, but as of right now it is not required and no standard set of tests has been adopted.

Dr. Coons said requiring molecular testing will make diagnoses more accurate and having a standard molecular diagnostic algorithm may make diagnoses faster and cheaper.

“We only had some of the tests that we needed, and we hadn’t had time to evaluate the newer tests until just recently,” he said.

Barrow neuro-oncologist Dr. Christopher Dardis said molecular classification is not likely to affect the standard therapeutic approach in the near future because most drugs used to treat gliomas are not designed to target a specific molecular subtype. However, he noted molecular classification will be crucial to the design of future clinical trials.

“It allows us to control for these potentially confounding variables and thereby to establish causality with a greater degree of certainty,” he said.

Already being used in clinical trials are drugs that specifically target a mutated form of the IDH1 enzyme, which is commonly seen in gliomas.

Dr. Coons said the proposed molecular classification system focuses on IDH mutations, as well as several others.

Dr. Coons said the presence of these abnormalities in different types of gliomas, their association with prognosis, and the availability of reliable and easy-to-perform testing suggested they could form the basis for a molecular classification system.

“The routine incorporation of markers for specific genetic mutations does lead to the possibility of some degree of targeted therapy,” Dr. Dardis said. “We hope that this will improve the quality and quantity of life for patients in due course. The presence of certain mutations may also influence the choice of more established therapies, although more work also remains to be done in this area.”

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