Understanding Molecular Testing for Glioma: How it Can Guide Your Diagnosis and Treatment

Molecular testing is considered the standard of care (something all patients need and should get) when diagnosing and treating gliomas.

Why Molecular Testing Matters?

Dr. Burt Nabors, a neuro-oncology expert at University of Alabama Birmingham (UAB) Medicine in Birmingham, Alabama, tells SurvivorNet that molecular testing matters for glioma patients for a number of reasons — it helps with diagnosis, prognosis, and treatment plan.

Diagnosis

Molecular testing has helped doctors identify more specific categories for glioma — and these categories help them decipher the best approach to cancer care.

“In 2016 we began to increasingly incorporate molecular diagnostics into how we categorize different types of brain cancer. Unfortunately, years before that we probably had a lot of tumors that were not the same, but we called them the same thing,” Dr. Nabors says.

“An example would be a glioblastoma versus an astrocytoma, These are two different biological entities. Prior we called them the same thing, but now they are in two separate categories, have their own treatments and have their own classification.”

Prognosis

Gliomas are a diverse group of tumors, and they are classified based on their grade (how aggressive they are) and molecular features. These features can help doctors offer patients and their families a more accurate prognosis.

“We’re in a space where it’s very difficult for medicine to cure brain cancers and our goals are typically revolving around preserving neurological function and helping people to live longer,” Dr. Nabors says. “…Often that’s information that we would try to share with patients and their families if feasible.”

Traditional diagnostic methods, like looking at tumor cells under a microscope, are important — but they have limitations.

This testing provides additional molecular-level information that can refine the diagnosis. For example, certain mutations, like those in the IDH1 or IDH2 genes, can distinguish between different types of gliomas and provide clues about how aggressive a tumor might be.

Treatment Plan

One of the most exciting aspects of molecular testing is its ability to tailor treatments to individual patients. By identifying specific mutations or genetic changes in the tumor, doctors can determine which treatments are most likely to work.

“Some brand new drugs called IDH inhibitors, are specifically relevant to patients who have a mutation and a gene called IDH,”  Dr. Nabors explains.

Targeted therapies, like IDH inhibitors, can slow tumor growth even further in patients with this specific mutation. Without molecular testing, doctors wouldn’t know if these treatments are suitable for their patients.

What is Molecular Testing?

Molecular profiling, or testing, is actually utilizing various tests — one of the tests is next generation sequencing — to generate a genomic profile for the cancer, as well as identify important biomarkers that can define diagnosis, prognosis, and predict response to treatment.

This should be part of discussions between you and your healthcare team after a cancer diagnosis.

Next-generation sequencing is a super advanced tool that has changed how we study genes. It’s like a modern toolbox used by scientists to quickly and affordably read the instructions of an organism’s DNA or RNA. This has helped researchers read a lot of genetic information quickly — so they can understand entire sets of genes, find differences in genes, and study how genes work.

NGS has various names, which can be a bit puzzling. NGS is the same as next-generation testing, comprehensive genomic profiling, broad molecular profiling or high-throughput sequencing. It is also commonly referred to as molecular testing.

What Types of Molecular Testing Are There?

Several molecular testing techniques are used on tissue samples. One method is antibody staining, where pathologists stain the tumor with an antibody to look for the presence of the IDH mutant protein.

Gliomas can either have a normal IDH gene (known as IDH wild-type) or carry the IDH mutation.

Tumors without the mutation will not be visible with the stain. However, tumors that have the IDH mutation will stain or show a color that pathologists can recognize. This is a very common technique pathologists use for many tumor types.

Another method is molecular sequencing, which is a process where doctors examine the DNA of the tumor cells to find specific changes or mutations in the genes. Both techniques can confirm whether the IDH mutation is present in the tumor cells.

How is Molecular Testing Done?

Molecular testing is typically performed on a sample of tumor tissue. This tissue is obtained from either surgery or a biopsy. Pathologists conduct the testing; these doctors are specially trained to study the characteristics of tumor tissues.

Molecular testing is widely available throughout the country, making it accessible to most patients diagnosed with gliomas.

Questions to Ask Your Doctor

If you or a loved one has been diagnosed with a glioma be sure to discuss molecular testing with your treating team. Here are some questions to ask:

• Do you need both the tissue sample and blood samples for molecular testing?
• What specific mutations will you be testing for in my tumor?
• Do I have any genetic mutation that would change the course of my treatment?
• Am I eligible to receive targeted therapy? What about immunotherapy?
• Is there a clinical trial that would be relevant for me?

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