Brain tumours occur when normal cells become abnormal cells and the abnormal cells grow in an uncontrolled manner in the brain. Brain tumours include primary and secondary brain tumours. In primary brain tumours the normal cells become abnormal cells within the brain. In secondary brain tumours normal cells become abnormal cells in other parts of the body and travel to the brain through the bloodstream. Secondary brain tumours are also known as brain metastases.
Primary brain tumours begin in the brain and rarely spread outside of the brain. Primary brain tumours can be benign or malignant. Benign brain tumours grow slowly and may take years to cause symptoms. They can push into nearby structures but rarely invade into nearby structures. Malignant brain tumours grow quickly and more commonly invade nearby structures. Brain tumours that grow more quickly present with earlier symptoms. There are more than 100 different types of primary brain tumours.
Brain tumours are generally named after the type of cell they have arisen from. The most common primary brain tumours are Gliomas, they arise from the supportive cells in the brain (glial cells). Types of Gliomas include Astrocytomas, Oligodendrogliomas and Ependymomas. Astrocytes and Oligodendrocytes are responsible for supporting normal nerve cell (neuron) functioning. Ependymomas arise from cells that line the fluid filled cavities within the brain (ventricles). Cerebrospinal Fluid (CSF) flows through the ventricles and around the brain and spinal cord and is important for the normal functioning of the nervous system.
Secondary brain tumours (brain metastases) occur when abnormal cancer cells from other parts of the body spread to the brain. An example of this is when breast cancer cells travel from the breast through the bloodstream to reach the brain. Brain metastases are the most common type of brain tumours. Two thirds of all brain metastases occur in patients that have lung cancer, breast cancer or melanoma but brain metastases can be associated with a number of other cancers including kidney and gastrointestinal cancers (colon, rectum, stomach).
What are the Causes of Primary Brain Tumours?
Studies have shown that there are certain factors, called risk factors, that may increase the chance of developing a brain tumour. In most cases the cause of a brain tumour is unknown. However the following factors may increase an individual’s risk of developing a brain tumour.
- Age: Brain tumours are more common in children and older adults.
- Gender: Overall there are more men diagnosed with brain tumours than women. However a few types of brain tumours are more commonly found in women.
- Family history: It is estimated that 5% of brain tumours are linked to hereditary genetic conditions. Some of the genetic conditions associated with brain tumours include Von Hippel-Lindau disease, tuberous sclerosis, nevoid basal cell carcinoma syndrome, neurofibromatosis, Li-Fraumeni syndrome and Turcot syndrome. Researchers have also identified “clusters” of brain tumours in some families without a history of one of the hereditary genetic conditions listed above.
- Ionising radiation: Previous exposure to ionising radiation (x-rays or CT scans) to the brain or head can increase the risk of brain tumours.
- Electromagnetic fields: Current research has shown conflicting results. Electromagnetic fields from power lines and mobile phones may or may not increase the risk of brain tumours. The use of hands-free headsets for adults and children and limiting mobile phone use has been recommended by the World Health Organisation (WHO).
- Chemicals and pesticides: It is possible that exposure to pesticides, vinyl chloride, rubber, oil products and/or solvents may increase the risk of brain tumours. However to date there is no strong evidence to supports this.
- N-nitroso compounds: Some studies suggest that dietary N-nitroso compounds may increase the risk of childhood and adult brain tumours. N-nitroso compounds are made in the body from nitrites or nitrates found in cigarette smoke and some cosmetics and cured meats. No definite link has been made and further research is needed.
- Epstein-Barr Virus (EBV): EBV is better known as the virus that causes mononucleosis or “mono”. Infection with EBV increases the risk of brain lymphoma (a less common primary brain tumour).
- History of head injury: There are some studies showing a link between severe head trauma and some brain tumours.
- Seizures: Seizures are associated with brain tumours but brain tumours can cause seizures. At this stage, it is not known if seizures increase the risk of brain tumours or if seizures occur because of the brain tumour. Further research is needed to determine if seizures increase the risk of developing a brain tumour.
- Exposure to nerve agents: One study has shown a link between nerve agents and an increased risk of brain tumours in Gulf War Veterans. Further research is needed.
What are the Symptoms of Brain Tumours?
Brain tumours can present with a wide range of symptoms and the severity of the symptoms varies from patient to patient. Symptoms may include one or more of the following:
- Nausea and/or vomiting
- Muscle weakness and/or altered sensation
- Difficulty with balance and/or coordination
- Memory or thinking problems
- Personality changes
- Vision changes (examples include double vision or vision loss)
- Language problems
A number of other conditions can cause these symptoms. It is important to tell your doctor if you experience any of these symptoms.
What are the Treatments for Primary Brain Tumours?
The recommended treatment for a primary brain tumour and the expected outcome from treatment (prognosis) depends on a number of factors including the type of brain tumour and its appearances under the microscope. As part of the initial work-up, imaging of the brain with a CT and/or MRI is performed. The images of the brain give doctors important information about the location of the tumour and whether the tumour can be safely removed with surgery.
The information below serves as an overview outlining the potential treatment options for primary brain tumours. Doctors will create an individualised plan for each patient. The individualised plan is based on the type of brain tumour (e.g., astrocytoma, ependymoma, etc), the grade of the tumour (the appearances under the microscope), the location of the brain tumour and the overall health of the patient. In some cases additional testing of the brain tumour is performed examining for specific mutations and proteins on the surface of the cancer cells. This additional information can also guide treatment.
Surgery is important in the diagnosis and treatment of brain tumours. Surgery may include a targeted biopsy, which involves a sampling of the tumour cells in the brain. The cancer cells are studied under the microscope. The type of brain tumour is identified and is graded from low grade to high grade. Low grade tumours tend to grow more slowly and are less aggressive compared to high grade tumours. Depending upon the type of the tumour, additional tests may be performed for specific markers that may guide additional treatments after surgery.
Surgery may also include debulking which is aimed at removing as much of the tumour as safely possible. Sometimes surgical debulking is not possible if the tumour is in a part of the brain where surgery is too risky, the tumour is too large for surgery, or the patient is not well enough for surgery.
Radiation therapy is a localised treatment that uses high energy x-rays (photons) to kill cancer cells. Radiation therapy may be recommended depending on the type of brain tumour, the grade of the tumour and whether or not the tumour can be completely removed with surgery. In some cases radiation therapy is delivered within weeks after surgery and in other cases it is recommended only if the tumour returns after surgery.
In cases where radiation therapy is recommended after surgery, the high energy x-rays are focused on the remaining tumour. If the tumour has been completely removed with surgery and immediate radiation therapy is recommended, the high energy x-rays are focused to the site where the tumour was removed (tumour bed).
External Beam Radiation Therapy (EBRT) is the most common type of radiation therapy used in brain tumour treatment. It is usually delivered once a day, five days a week. The total length of treatment can range from 3 to 6 ½ weeks. In many cases the patient will be asked to wear a customised mask during each radiation treatment. The mask reduces patient movement during treatment and ensures that the radiation treatment is targeting the cancer and avoiding important structures nearby.
Systemic therapy refers to the use of medications (tablets or injections) that include chemotherapy and/or biological therapy, also known as ‘targeted’ therapy. Systemic therapy may be recommended for some brain tumours after surgery. Chemotherapy may be given on its own or with radiation therapy. In other cases systemic therapy may be recommended if a brain tumour returns after surgery or radiation therapy.
What are the Treatments for Brain Metastases?
Brain metastases occur when cancer cells from other parts of the body spread to the brain. It is important for doctors to determine where the cancer originated from (for example breast, lung, etc). Some patients may have a history of cancer but for other patients, doctors need to identify where the cancer has come from using additional blood tests and imaging. Imaging of the brain with a MRI and/or CT will provide information on the number of tumours in the brain and their location within the brain.
Additional imaging of the body may be performed to determine whether the cancer has spread to other organs in the body including the liver, lungs and bones. The treatment of brain metastases will depend on a number of factors. These factors include where the cancer originated from, if other organs outside of the brain are involved, how many brain metastases are in the brain, where the brain metastases are located and their size and the patient’s overall health.
Localised treatment of brain metastases includes surgery and targeted radiation therapy (Stereotactic Radiosurgery). Surgery or stereotactic radiosurgery may be recommended if there is a limited number of brain metastases and there is no tumour outside of the brain (or the tumour outside of the brain is well controlled with systemic treatment). Stereotactic radiosurgery is used after brain surgery as well.
Radiation therapy to the whole brain (whole brain radiation therapy) is used occasionally if there are multiple brain metastases and/or cancer located outside of the brain is not well controlled. Whole brain radiation therapy is delivered one treatment a day, five days a week, over 1-2 weeks. Whole brain radiation therapy may also be considered after surgery or stereotactic radiosurgery to reduce the risk of brain metastases returning within the brain.
It is important to understand that surgery, stereotactic radiation therapy and whole brain radiation therapy can be used in combinations depending on the situation. The key difference between whole brain radiation therapy and stereotactic radiation therapy is that whole brain radiation therapy can have more cognitive side effects (although this is still not common) but better control of tumours within the brain, while stereotactic radiation therapy has less cognitive issues but only treats specifically what can be seen, (with generally an excellent effect) so there is a risk of tumours elsewhere in the brain occurring that the radiation therapy has not treated.
What are the Side Effects of Radiation Therapy?
The potential side effects of radiation treatment are divided into acute side effects (can occur during and shortly after radiation treatment) and late effects (can occur months to years after radiation treatment and are permanent).
Side effects during/soon after treatment (Early or ‘acute’ side effects)
General – Fatigue is quite common in the second half of treatment and is very variable between patients. Fatigue may persist for several weeks after treatment.
Local – The other side effects of radiation therapy come from the structures/organs in and just next to where the radiation is being targeted. These side effects appear half way through treatment and increase in severity toward the end of treatment. Due to the cumulative nature of these side effects they can peak in severity 7-10 days following treatment.
Skin reddening and irritation – The skin on the scalp may become red, dry and/or itchy. Usually the skin reaction is mild to moderate.
Loss of hair (alopecia) – Hair loss may be partial or total depending on the treatment. The hair loss can be temporary or permanent depending on the amount of radiation.
Cerebral oedema (swelling in the brain) – Radiation therapy can cause temporary inflammation around the brain tumour. This may cause headaches, nausea, vomiting and/or drowsiness. If these symptoms occur during treatment, corticosteroid medication may be used to treat these symptoms. Inflammation may also temporarily worsen pre-existing neurological symptoms.
Tinnitus (ringing in the ears) and hearing loss – These symptoms are uncommon during radiation treatment.
What can help reduce acute side effects?
Resting as needed can help with fatigue. Creams can be used on the scalp for skin reddening and irritation. Wigs can be used for temporary or permanent hair loss. If headaches, nausea and/or vomiting occur during treatment, corticosteroid medication may be used to reduce the swelling around the tumour, which usually improves symptoms. Pain medications and anti-nausea medications are prescribed if needed.
Early-delayed side effects (side effects occurring 1-6 months after treatment)
Somnolence syndrome- this is uncommon but can occur 1-6 months following radiation treatment. Symptoms can include sleepiness, irritability, headaches, nausea, vomiting and loss of appetite. The symptoms usually resolve after a few weeks and corticosteroid medication may be used to treat symptoms.
Side effects well after treatment (Late or long-term side effects)
Late side effects may occur a few months to years after treatment. They are more rare than early side effects. Depending on the problem it may occur once and then go or may be more persistent over the long term or may come and go over time. The likelihood of developing late side effects from radiation treatment depends on the amount of radiation and the relationship of the brain tumour to important structures located nearby. Your Radiation Oncologist will explain the potential late side effects of your treatment and how to manage potential side effects in more detail.
General – Neurocognitive effects include changes that can affect thinking, learning, processing or remembering information. Neurocognitive effects may also occur following surgery and/or chemotherapy.
Local – If the tumour is located close to the following structures, uncommon side effects may occur.
Eye and optic nerves – Radiation can cause the lens of the eye to become cloudy (cataract). This can cause painless visual impairment years after treatment. Radiation changes to the retina may be asymptomatic or cause painless loss of vision, which can be partial or total. Radiation to the optic nerves can very rarely cause permanent visual loss.
Ear – Hearing loss and ringing in the ear (tinnitus) can develop progressively over a few years following treatment and is usually permanent.
Pituitary gland – Radiation may cause the pituitary gland to become underactive. Your doctor may recommend blood tests following treatment to monitor for this.
Brain necrosis (tissue death) – This is a rare event occurring after high doses of radiation. It tends to occur 1-3 years post treatment. Symptoms depend on the location of the necrosis. It can be a very serious complication that may require surgical treatment.
Radiation induced cancers – Second cancers occurring as a result of radiation therapy are an extremely rare side effect of radiation therapy.
What can be done to treat late side effects?
Changes in vision following radiation treatment should be assessed to determine the cause. If radiation results in a cataract, the lens can be replaced with a minor operation. Radiation effects to the retina or optic nerve are generally irreversible. It is important to prevent and treat other medical conditions that can contribute to eye problems (diabetes). Hearing aids may be beneficial for hearing loss. If the pituitary gland becomes underactive, hormone replacement is prescribed. Medications may be useful for some neurocognitive changes that occur after radiation treatment. There are medications under investigation that may be helpful in preventing neurocognitive effects from radiation.
You should discuss management of any side effects with your medical team.
The best person to discuss radiation therapy for brain cancer with is a Radiation Oncologist. You can ask your Surgeon or General Practitioner for a referral to a Radiation Oncologist for a discussion about whether radiation therapy is a suitable treatment option for you.
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Page last updated: 01/12/20