Glioblastoma – Diagnostics – Overview of Information and Clinical Research

Glioblastoma is the most aggressive and most common type of cancerous brain tumor in adults, and diagnosing it accurately is the first critical step in planning treatment. Understanding when to seek medical attention and what diagnostic tests are involved can help patients and their families navigate this challenging time with greater confidence and clarity.

Introduction: When Should You Seek Diagnostic Testing?

Anyone experiencing persistent or worsening symptoms that affect brain function should seek medical attention promptly. Glioblastoma symptoms often come on quickly and can be mistaken for other conditions, which is why early evaluation is so important.^[1] The growing tumor puts pressure on healthy brain tissue, and this pressure causes many of the symptoms that bring people to the doctor.^[2]

You should consider seeing a healthcare provider if you experience persistent headaches that are particularly severe in the morning, as this is one of the most common early warning signs.^[1] Other symptoms that warrant medical evaluation include sudden or gradual changes in vision, such as blurred or double vision, unexplained nausea and vomiting, memory problems, personality changes, difficulty speaking, or new-onset seizures, especially in adults who have never had seizures before.^[1]^[2] Some people also experience weakness on one side of the body, problems with balance or coordination, or changes in sensation like numbness or tingling.^[2]

Because glioblastoma symptoms can resemble those of a stroke or other serious conditions, it is crucial to get a full medical workup from your doctor if you or a loved one experience these warning signs.^[8] The symptoms tend to worsen rapidly as the tumor grows, and in some cases can progress to unconsciousness if left untreated.^[4] Early diagnosis can make a significant difference in planning appropriate care and starting treatment as soon as possible.

⚠️ Important

An MRI scan alone cannot confirm a glioblastoma diagnosis. While the scan may show a mass in the brain that looks like glioblastoma, other conditions such as strokes, infections, or different types of tumors can appear similar on imaging. A biopsy or surgery to remove tissue is necessary to confirm the diagnosis.^[18]

Classic Diagnostic Methods for Identifying Glioblastoma

The diagnostic process for glioblastoma typically begins with a careful evaluation by a healthcare provider. This starts with a neurological examination, which is a physical exam that checks various functions controlled by the brain. During this exam, the doctor will test your vision, hearing, balance, coordination, strength, and reflexes.^[10] Problems in one or more of these areas can provide important clues about which part of the brain the tumor is affecting and help guide further testing.^[10]

Imaging Tests

If a brain tumor is suspected after the neurological exam, imaging tests are the next step. These tests create detailed pictures of the inside of the brain, allowing doctors to see the exact location and size of any abnormal growths.^[10]

Magnetic Resonance Imaging (MRI) is the most important and commonly used imaging test for diagnosing glioblastoma.^[6]^[10] An MRI uses powerful magnets and radio waves to create very detailed images of the brain’s soft tissues. Usually, images are taken both before and after the injection of a contrast dye into a vein. The contrast helps make the tumor more visible on the images. Glioblastomas typically show strong contrast enhancement and often have areas of dead tissue (called necrosis) in the center of the tumor.^[6] The brightness and pattern on the MRI can give doctors important information about the type and aggressiveness of the tumor.

In addition to standard MRI, doctors may use specialized imaging techniques to learn more about the tumor. Magnetic Resonance Spectroscopy (MRS) is a tool based on MRI technology that provides information about the chemical composition of the tumor.^[6] Different chemicals are present in different amounts in normal brain tissue compared to tumor tissue. For example, a chemical called choline is more abundant in tumors, while N-acetylaspartate (NAA) is more common in healthy brain. This technique works like a non-invasive tissue sampling, although it is not as definitive as an actual biopsy.^[6]

Computed Tomography (CT) scans may also be used to look for brain tumors, especially in emergency situations when quick imaging is needed.^[6]^[10] A CT scan uses X-rays and a computer to create three-dimensional images of the body. While not as detailed as MRI for viewing brain tissue, CT scans are faster and can be useful in certain situations.

Other advanced imaging tests may include Positron Emission Tomography (PET) scans, which can show how active the tumor cells are by measuring their metabolism.^[10] A special type called 18F-DOPA PET imaging can identify the most aggressive, metabolically active regions of the glioblastoma, which helps doctors plan treatment more precisely.^[13]

Biopsy: Confirming the Diagnosis

Imaging tests can suggest glioblastoma, but the only way to confirm the diagnosis is through a biopsy. A biopsy is a procedure in which a sample of the tumor tissue is removed and sent to a laboratory for examination under a microscope.^[10]^[18] This can be done with a needle before surgery or during surgery to remove the tumor.

A specialized doctor called a neuropathologist examines the tissue sample to determine whether the cells are cancerous and, if so, what type of brain tumor it is.^[8] The pathologist looks at the appearance of the cells and the tissue structure. For glioblastoma, they need to see either the formation of new blood vessels within the tumor (called microvascular proliferation) or areas of dead cells (necrosis).^[15]

Molecular and Genetic Testing

Modern diagnosis of glioblastoma goes beyond just looking at cells under a microscope. The World Health Organization now classifies brain tumors primarily based on their molecular features — meaning the specific genes and proteins found in the tumor cells.^[15]

One of the most important genetic tests looks for mutations in the IDH1 or IDH2 genes. Glioblastomas typically do not have mutations in these genes, which is why they are called “IDH-wildtype” (the term “wildtype” means the gene is unchanged).^[9]^[15] This distinguishes glioblastoma from other types of brain tumors that do have IDH mutations and generally have a better outlook.

Another important test is the MGMT methylation test. MGMT is a protein that can repair DNA damage caused by chemotherapy.^[9] If the MGMT gene is turned off (methylated) in the tumor cells, the tumor cannot repair the damage from chemotherapy, which means the treatment is more likely to work. If MGMT levels are high (non-methylated), chemotherapy may be less effective.^[9] This information helps doctors predict how well the tumor will respond to treatment.

Additional genetic alterations that doctors may look for include changes in the TERT gene, the EGFR gene, and abnormalities in chromosomes 7 and 10.^[15] Through advanced genomic profiling, researchers have identified that glioblastomas have a very complicated genetic makeup, with changes in multiple signaling pathways that control cell growth and survival.^[5] Each glioblastoma is different from the next, which is why a personalized approach to treatment based on genetic testing is necessary.^[8]

Diagnostics for Clinical Trial Qualification

When considering participation in a clinical trial, patients typically undergo the same core diagnostic tests described above — neurological examination, MRI or CT imaging, and tissue biopsy with molecular testing. However, clinical trials often have specific eligibility criteria that require additional testing or documentation to ensure patients meet the study requirements.

The standard diagnostic approach still forms the foundation. Imaging with MRI is used to measure the size and location of the tumor, and this baseline measurement will be compared to future scans to see if the treatment is working.^[10] The tissue biopsy confirms the diagnosis and provides information about the tumor’s genetic characteristics, which many clinical trials use to select appropriate patients.

For example, some clinical trials may only enroll patients whose tumors have specific molecular features, such as MGMT methylation status or particular gene mutations.^[9] Other trials may require that patients have newly diagnosed glioblastoma rather than recurrent disease, or vice versa. Some studies focus on patients whose tumors are large and cannot be completely removed by surgery.^[14]

Blood tests are commonly required to check overall health and organ function before enrolling in a clinical trial. These tests ensure that patients are healthy enough to tolerate the experimental treatment and monitor for any side effects during the study.^[11] Specific blood tests might include blood cell counts to make sure the bone marrow is functioning properly, and tests of kidney and liver function to ensure these organs can process the medications.

Advanced imaging techniques may also be part of clinical trial protocols. For instance, trials testing new radiation approaches may use 18F-DOPA PET scans combined with MRI to map the most active regions of the tumor with high precision.^[13] This helps researchers target treatment more accurately and measure the response to therapy.

Some trials may require documentation of the patient’s functional status through standardized scales that measure how well they can perform daily activities and whether they have any neurological deficits. This information helps researchers understand the tumor’s impact on quality of life and track changes during treatment.

⚠️ Important

Genetic marker analysis of your tumor should be sent for testing after biopsy, as mutations may be present that help with prognosis and provide targets for therapy.^[8] What works for one glioblastoma patient may not work for another because each tumor has unique genetic characteristics. This personalized information is increasingly important for both standard treatment and clinical trial selection.

Prognosis and Survival Rate

Prognosis

Glioblastoma remains one of the most challenging cancers to treat, with a prognosis that is generally poor despite maximum treatment efforts.^[4]^[8] Several factors affect how the disease progresses and what outcomes patients can expect. Age at diagnosis plays an important role, with younger patients typically having better outcomes than older individuals. The average age at diagnosis is 64 years, though glioblastoma can occur at any age.^[2]^[5] Men are diagnosed slightly more often than women, and the disease is more common in Caucasians compared to other ethnicities.^[5]

The extent of surgical removal is another critical factor. Patients who undergo maximal safe surgical resection, where as much of the tumor as possible is removed without damaging critical brain functions, tend to live longer than those who cannot have surgery or have only partial removal.^[4]^[11] However, even with aggressive surgery, glioblastoma cannot be completely removed because microscopic tumor cells spread into surrounding healthy brain tissue.^[11]

Genetic characteristics of the tumor significantly influence prognosis. Tumors with MGMT methylation (meaning the gene is turned off) tend to respond better to chemotherapy and have improved survival compared to those without this feature.^[9] Patients with secondary glioblastomas, which develop from lower-grade tumors over time, generally have better outcomes than those with primary (de novo) glioblastomas that appear suddenly.^[5]

Unfortunately, despite all available treatments, glioblastoma almost always comes back.^[3]^[7] The tumor is inherently resistant to current therapies, and the difficulty in completely removing all cancer cells means that recurrence is virtually inevitable.^[7] When the tumor recurs, it is always fatal.^[7]

Survival Rate

The typical survival time after diagnosis of glioblastoma is 10 to 13 months with treatment, though individual outcomes vary.^[4] According to recent studies, approximately 56% of patients in some treatment programs survive 12 months, with a median overall survival of about 13.1 months.^[13] Other sources report median survival of approximately 21 months with the most current standard treatments.^[7]

Longer-term survival remains uncommon. Approximately 40% of patients survive the first year after diagnosis, but this drops to about 17% in the second year.^[6] The five-year survival rate is poor, ranging from 5% to 13% depending on the study and patient population.^[4]^[11] Fewer than 5% to 10% of people survive longer than five years overall.^[4]

Without any treatment, survival is typically only about three months.^[4] Even with the standard approach of surgery followed by radiation and chemotherapy, glioblastoma can result in death in as little as six months in some cases, making it imperative to seek expert care immediately.^[6]^[8]

Patients whose tumors have favorable genetic characteristics may live longer. For instance, in some treatment programs, patients with specific tumor genetics had median survival extending to 22 months.^[13] These statistics underscore the importance of molecular testing to understand each patient’s unique tumor profile and potential response to treatment.