What to Know About Glioma Type and Grade
- Gliomas are brain tumors that start in the brain’s support cells, called glial cells. Doctors now use genetic testing, including checking for IDH mutations and other molecular markers, to better understand a tumor’s behavior and guide treatment.
- The three main types of glioma diagnosed in adults include astrocytoma, oligodendroglioma, and glioblastoma. Astrocytoma and oligodendroglioma are both IDH mutant, which means they have changes in the IDH gene. Glioblastoma is IDH wildtype, which means it does not have changes in the IDH gene.
- Glioblastoma is the most aggressive type of adult glioma.
- Advances in genetic testing are helping doctors match patients with more personalized treatments. In 2024, the FDA approved vorasidenib (Voranigo) for certain patients with IDH-mutant gliomas, marking an important step forward.
- “It’s really becoming a precision field, precision oncology, where if we know a specific mutation, instead of just giving the same treatment to everybody, we will tailor the treatment to a specific glioma, which was not possible 10 or 20 years ago,” Dr. Yoshua Esquenazi, director of surgical neuro-oncology at McGovern Medical School at UTHealth Houston, tells SurvivorNet.
“We don’t call every glioma the same way. They’re very different,” says Dr. Yoshua Esquenazi, director of surgical neuro-oncology at McGovern Medical School at UTHealth Houston.
Read MoreThe Three Main Types of Glioma
Each type also gets a grade from 2 to 4. A higher grade generally means a more aggressive tumor, and grades compare tumors within the same type, according to the medical journal Pathology and Translational Medicine.
The three types of glioma diagnosed in adults include:
- Astrocytoma, which is IDH mutant
- Oligodendroglioma, which is IDH mutant
- Glioblastoma, which is IDH wildtype (does not have changes in the IDH gene)
The term “glioblastoma” is now reserved for IDH-wildtype tumors. An IDH-mutant astrocytoma is not called glioblastoma even at grade 4. All glioblastomas are considered grade 4, though.
Glioblastoma is, in Dr. Esquenazi’s words, “the more aggressive one” and “unfortunately is one of the most common tumors.”
However, glioblastoma patients do tend to be older, Dr. Esquenazi says, typically around 50 to 70 years old.
Glioma symptoms
Because gliomas can press on different areas of the brain and spinal cord, they can cause a range of symptoms, from to headaches to seizures.
“If you have a tumor in the language area, then the patient will have language problems,” Dr. Esquenazi says. These can present as problems speaking.
“If it’s in the visual area in the occipital lobe, they may have some vision problems,” he adds.
Likewise, tumors in motor or sensory areas can cause difficulty moving an arm or leg, or changes in sensation.
The IDH Dividing Line
Tumors once grouped together as “lower grade” are now split by biology.
“We used to categorize them as lower grade, but now we divide them because of a specific mutation called the IDH mutation,” Dr. Esquenazi explains.
IDH-mutant astrocytomas can be grade 2, 3, or 4, while oligodendrogliomas are grade 2 or 3. As Dr. Esquenazi notes, a lower grade generally means a better prognosis, and grade 3 tumors are more invasive and aggressive.
The focus on IDH mutation has allowed doctors change how they manage low-grade gliomas.
“This is a mutation that defines these tumors,” Dr. Esquenazi explains. “This is a somatic mutation that leads to those tumors, particularly the IDH mutant astrocytoma and the IDH mutant oligothendroglioma. And these patients can [now] take a pill once a day,” that has been shown to delay tumor progression.
Targeted Treatment: Where the Field Is Heading
As Dr. Esquenazi notes, IDH mutation status can now help doctors determine the best treatment approach.
In August 2024, the FDA approved vorasidenib (Voranigo), an oral, brain-penetrant inhibitor of mutant IDH1 and IDH2, for patients 12 and older with grade 2 astrocytoma or oligodendroglioma with a susceptible IDH1 or IDH2 mutation following surgery.
It was the first systemic therapy approved for this population.
In the phase 3 INDIGO trial, patients on vorasidenib had a 61% lower risk of progression or death than those on placebo, according to the American Association for Cancer Research (AACR).
Vorasidenib’s approval covers only tumors with a susceptible IDH1 or IDH2 mutation. Molecular testing of tumor tissue, obtained by biopsy or resection, determines eligibility.
The WHO CNS5 categorization system relies on IDH status, 1p/19q codeletion, and select molecular markers to establish both diagnosis and grade.
“There are other medications that can target other mutations such as EGFR inhibitors or BRAF inhibitors,” Dr. Esquenazi adds. “There are some gliomas that can have other mutations like a BRAF B600 mutation or some of the midline gliomas, the H3K27 mutation … there is now a specific medication that can target that mutation.
“It’s really becoming a precision field, precision oncology, where if we know a specific mutation, instead of just giving the same treatment to everybody, we will tailor the treatment to a specific glioma, which was not possible 10 or 20 years ago,” he adds.
Questions To Ask Your Doctor
- What type of glioma do I have?
- Am I a candidate for an IDH inhibitor?
- What IDH inhibitor side effects should I be aware of?
- Are there any clinical trials I should consider joining?
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