How Deadly is a Brain Tumor? Now the DNA Can Tell

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By Maggie Fox

Researchers have come up with a new way of classifying brain tumors that can more accurately predict how serious one is, and that may lead to better drugs for treating them.

The new method looks at the specific DNA mutations that characterize a tumor — in this case a type of brain tumor called a glioma.

Two studies published in the New England Journal of Medicine show that it’s way too general to just call a brain tumor by the type of tissue involved. As with other cancers, it’s clear that it’s not so much where the tumors first form that matters, but what kind of genetic mutation caused them to form.

"This molecular data helps us better classify glioma patients, so we can begin to understand who needs to be treated more aggressively and who might be able to avoid unnecessary therapies," said Dr. Daniel Lachance, a neuro-oncologist at the Mayo Clinic.

"This molecular data helps us better classify glioma patients."

About 23,000 Americans develop a brain tumor each year — and 10,000 of those are gliomas — and about 14,000 die of them.

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"This genome-wide analysis will be much more objective and likely will be practice-changing," said Dr. Andrew Sloan, director of the Brain Tumor and Neuro-Oncology Center at Case Western Reserve University School of Medicine. "It can be easily implemented and will markedly improve diagnosis, patient care and treatment planning."

With gliomas, like other types of cancers, patients now get a diagnosis based on the type of brain cells affected — glial cells — and on how the tumor cells look to a pathologist under a microscope.

But it’s an inexact approach.

The new method provides for three categories of glioma.

"We looked at the six most common forms of glioma and were able to deduce that these can be effectively grouped into three distinct molecular super clusters of lower-grade gliomas," said Dr. Roeland Verhaak of the MD Anderson Cancer Center in Houston.

One type of glioma looks more like a far-deadlier type of brain tumor called a glioblastoma. Patients with this type of tumor lived only on average a little over a year, worse even than the average 1.7 years for a glioblastoma patient.

Patients with a second type of glioma lived about 6.3 years on average and those with a third type lived eight years after diagnosis on average.

"These markers will potentially allow us to predict the course of gliomas more accurately, treat them more effectively and identify more clearly what causes them in the first place," said Margaret Wrensch of the University of California San Francisco.

“These markers will potentially allow us to predict the course of gliomas more accurately."

"The findings demonstrate that these three groups of low-grade gliomas can be identified objectively by three different markers," Sloan added.

Gliomas are usually treated with surgery, radiation therapy and chemotherapy. Most of the time, doctors cannot predict how aggressive a glioma is going to be.