The brain is one of the largest and certainly the most complex organ in the human body. At cellular level, the brain is primarily composed of two types of cells – the more than 100 billion nerve cells called neurons, which are linked and communicate with other neurons through trillions of connections, and glial cells. (Glia is the Greek word for glue, although the glia cells are more than just connective tissue.) The glial cells provide structural and metabolic support, provide insulation, plays a role in the forming of the protective sheath (the myelin) around the axons linking the neurons, as well as playing a role, along with neurons, in the communication processes in the central nervous system.
The complex structure of the brain is unfortunately not exempt from the effects of cancer and there are more than 120 different types of brain and central nervous system tumors. Not all of the most common brain tumors originate in the brain. The most aggressive brain tumor is called glioblastoma, which originates in the glial cells in the brain.
The four most common brain tumors:
- Glioblastoma is the third most common of all brain tumors but the most common primary (originating in the brain) tumor, forming in the glial cells in the brain.
- Metastatic is the most common brain tumor but is a secondary brain tumor, meaning it originates from cancer elsewhere in the body, which then spreads to the brain.
- Astrocytoma is a primary brain tumor that originates in star-shaped cells called astrocytes, which are a sub-type of glial cells.
- Meningioma is technically not a brain tumor, as these tumors form in the meninges, the membranes that line the skull and vertebral canal. Their growth may affect the brain.
Characteristics of glioblastoma:
Glioblastoma is a malignant tumor that starts as a growth of cells in the glial cells in the brain or spinal cord and can also evolve from lower-grade astrocytoma. It grows rapidly and aggressively and can spread throughout the brain, invading and destroying healthy brain cells. It occurs most often in the frontal and temporal lobes in the brain. If left untreated, glioblastoma is a devastating brain cancer that can result in death within six months. It is one of the most complex, deadly, and treatment resistant cancers.
More men than women are diagnosed with glioblastoma and the mean age of diagnosis is 64 years. Treatment can help but survival is poor with about 40% survival in the first year after diagnosis and 17% in the second year. The five-year survival rate for patients is only about 7%. Glioblastoma is estimated to account for almost half of all cancerous brain tumors.
Glioblastoma is one of the most expensive cancers to treat and the cancer growth, along with its harsh treatments, can inflict devastation upon the brain with the patient losing a host of functions controlled by the brain, amongst others affecting the ability to work or drive.
It is not known why some people develop cancerous brain tumors and while treatment can ease symptoms and prolong life, there is no cure for glioblastoma.
Glioblastoma symptoms:
Symptoms of glioblastoma can vary, depending on where it is located, and can include any of the following symptoms:
- Headaches that are persistent and keep getting worse.
- Nausea and vomiting.
- Loss of appetite.
- Drowsiness.
- Blurred or double vision.
- Seizures.
- Changes in mood and personality.
- Changes in the ability to think and learn.
- Memory problems.
- Gradual onset of speech difficulty.
- Muscle weakness or balance problems.
- Changes in sensation, numbness, or tingling.
Diagnosis:
Modern sophisticated imaging techniques are used to accurately determine the location and nature of brain tumors, with the main diagnostic tools being:
- Computed tomography such as CT (also known as CAT) scans are done by X-ray procedure.
- Magnetic resonance imaging (MRI scan) is used to identify the anatomically location of a tumor.
- Magnetic resonance spectroscopy (MRS) utilizes the same MRI equipment to examine the tumor’s chemical profile by comparing the chemical composition of normal brain tissue with abnormal brain tissue. It works on the principle that certain chemicals are abundant in the normal brain, while others are abundant in tumors, such as choline. It is used to determine the tumor type and aggressiveness.
Once a brain a brain tumor is detected, a neurosurgeon would do biopsy to remove tissue from the tumor for examination by a medical pathologist. Analysis of the tumor tissue can determine the type of tumor and whether there are signs of rapid growth in the tumor cells to determine the grade and stage of the tumor.
The grade describes the appearance of cancerous cells. Most tumors are graded 1,2,3, or 4. In grade 1 tumors, the cells look close to normal. The higher the grade, the more abnormal the cells look. The grade allocation is an indication of how quickly the cancer cells are likely to grow. Glioblastomas are all grade 4, which means they are fast growing cancerous tumors.
The stage of cancer describes the size of a tumor and how far it has spread from the spot where it originated.
- Stage 1 – the cancer is localized to a small area and has not spread.
- Stage 2 – the cancer has grown, but it hasn’t spread.
- Stage 3 – the cancer has grown larger and has possibly spread.
- Stage 4 – the cancer has spread to other areas.
Glioblastoma treatment:
While there is no cure for glioblastoma, treatments might slow cancer growth and reduce symptoms. Due to the localization of tumors in the brain, treatment is challenging. The main treatments for glioblastomas are surgery; radiotherapy which uses high energy x-rays to destroy cancer cells; and chemotherapy which uses cytotoxic drugs to destroy cancer cells. These treatments may be used on their own or as a combination of treatments. Supportive treatments may also be given to help control the symptoms.
Surgery is the main treatment for glioblastoma and surgeons will try to remove as much of the tumor as possible without injuring the surrounding normal brain tissue, which can help slow down the progression of the tumor and relieve the symptoms. The option of surgery depends on where the tumor is situated in the brain and on whether the patient is well enough to undergo surgery. As glioblastomas are surrounded by migrating tumor cells which have invaded surrounding tissue, it is not possible to surgically remove the tumor entirely. By removing the bulk of the tumor, the cells in the center of the tumor that may be resistant to radiation and/or chemotherapy are reduced.
Radiation therapy can start once the operating wound has healed, aiming to selectively kill the remaining tumor cells which have invaded surrounding brain tissue. Multiple sessions of radiation are delivered to the tumor and the surrounding zone with infiltrated tumor cells. While each treatment also induces damage to healthy tissue, most of the normal cells repair the damage before the next treatment, while tumor cells do not self-repair. Depending on the type of tumor, treatments are repeated for 10 to 30 times, usually once a day for five days a week. Radiation therapy provides improved outcomes and longer survival rates than surgery alone.
Chemotherapy consists of special drugs that are designed to kill tumor cells and are usually administered after surgery, as well as during and after radiation therapy. Chemotherapy medication circulates in the blood with the aim to kill cancer cells.
Supportive care, also known as palliative care, primarily focusses on pain relief and treatment of other symptoms.
Conclusion:
Glioblastoma is the most aggressive type of brain cancer that is very challenging to treat. While there is no cure, treatments can help to ease symptoms and prolong life.
Coping with a diagnosis of a brain tumor can be difficult, especially if it is a fast-growing tumor. For more information on how to deal with such a diagnosis, please see the Health Insight blog: Running out of time.
References:
Glioblastoma. Published 10 January 2023. Mayo Clinic. USA. (www.mayoclinic.org)
Glioblastoma multiforme. Published online. American Association of Neurological Surgeons. (www.aans.org)
Glioblastoma. Reviewed 7 June 2023. Cancer Research UK. (www.cancerresearchuk.org)
Coping with brain tumors. Reviewed 28 April 2023. Cancer Research UK. (www.cancerresearchuk.org)
About glioblastoma. Published online. National Brain Tumor Society, USA. (www.braintumor.org)
Glioblastoma (GBM). Reviewed 3 September 2021. Cleveland Clinic. USA. (www.clevelandclinic.org)
What are the most common types of brain tumors? Published 5 November 2018. Neuroscience Blog. Penn Medicine. University of Pennsylvania. (Academic Medical Center.) USA. (www.pennmedicine.org)
HEALTH INSIGHT
October 2023