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Glioblastoma is the most common primary brain cancer, or cancer that starts in the brain, with around 12,000 cases diagnosed in the United States each year. All glioblastomas are grade IV brain tumors, meaning they contain the most abnormal looking cells and are the most aggressive.
How does glioblastoma start?
Glioblastoma develops from astrocytes, star-shaped brain cells that help protect the brain from diseases in the blood and provide the brain’s neurons with nutrients.
Astrocytes themselves are a type of glial cell. Glial cells supply nutrients to the brain and give the brain its physical structure. They also insulate neurons from each other and create a stable chemical environment in the brain.
Although glioblastoma can start anywhere in the brain, it most commonly forms in the frontal lobe and the temporal lobe. The frontal lobe is located near the forehead and plays important roles in speech, voluntary movement, behavior and memory. The temporal lobe sits toward the bottom of the brain and forms new memories, processes language, and processes input from the senses of hearing, sight, taste and touch.
What’s the prognosis for glioblastoma?
There is currently no cure for glioblastoma. The median length of survival after a diagnosis is 15-18 months, while the disease’s five-year survival rate is around 10%. Though all glioblastomas recur, initial treatments may keep the tumor controlled for months or even years.
Glioblastoma statistics reflect many of the challenges in treating the disease.
As glioblastoma grows, it forms microscopic branches that can spread into different parts of the brain. These branches makes it nearly impossible to remove the entire tumor with surgery. In addition, a single tumor contains many different types of cells, so a drug that works for some cells may not successfully treat the entire tumor.
Brain tumors in general are hard to treat, as well. When removing tumors in other parts of the body, surgeons often take out a small section of healthy tissue surrounding the tumor, referred to as a margin. They do this to remove cancer cells that are not visible to the naked eye. Removing healthy brain tissue is much more difficult, since tissue near a tumor may control essential functions, such as speech, language and movement. During brain surgery, neurosurgeons strive to remove as much of the tumor as possible without damaging the parts of the brain that control these functions.
Delivering medications to the brain is also difficult. The blood vessels for the central nervous system (CNS) are designed to stop diseases and toxins in the blood from reaching this area, which includes the brain and spinal cord. Known as the blood brain barrier, this feature protects the brain, but it also stops many drugs from getting to brain tumors.
While glioblastoma is difficult to treat, clinical trials are exploring new radiation therapy, chemotherapy and immunotherapy strategies to fight this disease. Other trials are designed to improve patients’ quality of life and lessen the burden of the disease and its treatments.
What are the risk factors for glioblastoma?
Anything that increases the chance of developing a particular disease is a risk factor.
Doctors have only identified a few risk factors for glioblastoma. The most significant is prior radiation to the head. People often receive radiation to the head to treat other cancers near the brain or cancers that have or may spread to the brain.
A few hereditary cancer syndromes are also connected to glioblastoma. These include Li Fraumeni syndrome, neurofibromatosis type 1 and Turcot syndrome.
In addition, this cancer tends to develop more often in men, people age 50 or older, and Caucasians.
What are the symptoms of glioblastoma?
Like all brain tumors, the symptoms of glioblastoma depend on the area of the brain where the tumor begins and spreads, as well as how quickly the tumor grows. Glioblastoma can:
- • Invade and destroy brain tissue
- • Put pressure on nearby tissue
- • Take up space and increase pressure within the skull. This symptom is known as intracranial pressure.
- • Cause fluids to accumulate in the brain tissue
- • Block the normal circulation of cerebrospinal fluid through the spaces within the brain
- • Cause bleeding
Brain tumor symptoms vary from person to person. They may include:
- Headaches: These are often the first symptoms of glioblastoma. Brain tumor headaches can differ from normal headaches. They typically become more frequent over time and may not respond to over-the-counter pain medicine. They may cause nausea or vomiting and can get worse when you lie down, bend over or bear down, such as when you have a bowel movement.
- Seizures: Seizures can take many different forms. While most people associate seizures with uncontrollable arm and leg movements and a loss of consciousness, symptoms can be subtler. Other seizure symptoms include numbness, tingling, difficulty speaking, strange smells or sensations, staring and unresponsive episodes.
- Changes in mental function, mood or personality: Brain tumors can cause people to become withdrawn, moody or inefficient at work. They may feel drowsy, confused and unable to think. Depression and anxiety, especially if either develops suddenly, may be an early symptom of a brain tumor. Brain tumors may also cause behavior changes, including a loss of inhibitions.
- Changes in speech: People with brain tumors may have trouble finding words, speak incoherently, and be unable to express or understand language.
- Sensory changes: Changes in the ability to hear, smell or see, including double or blurred vision can be symptoms of a brain tumor. The sense of touch can also be impacted. People with brain tumors may lose some of their ability to feel heat, cold, pressure, sharp edges or light touches.
- Loss of balance or coordination
- Changes in pulse and breathing rates: This symptom usually occurs with a brain tumor compresses the brain stem, which controls basic bodily functions including breathing and the heart rate.
These symptoms do not always mean you have a brain tumor. However, it is important to discuss any symptoms with your doctor, since they may signal other health problems.