Potential side effects of radiation therapy for brain and spinal cord cancer
Side effects can occur with any type of treatment for brain and spinal cord cancer, but not everyone has them or experiences them in the same way. Side effects of radiation therapy will depend mainly on the:
- size of the area being treated
- total dose
- treatment schedule
Radiation therapy damages cancer cells, but healthy cells in the treatment area can also be damaged, even though steps are taken to protect them as much as possible. Different cells and tissues in the body tolerate radiation differently.
Side effects can happen any time during, immediately after or a few days or weeks after radiation therapy. Most side effects go away after radiation therapy is finished. Late side effects can occur months or years after radiation therapy. Some side effects may last a long time or be permanent.
It is important to report side effects to the healthcare team. Many side effects can be relieved by medications, a change in diet or other measures. Doctors may also grade (measure) how severe certain side effects are. Sometimes radiation therapy treatments need to be adjusted if side effects are severe.
Fatigue is one of the most common side effects of radiation therapy. Fatigue may be caused by anemia or poor appetite. It may also be related to toxic substances that are produced when cancer cells break down and die. During radiation therapy, the body uses more energy to heal itself, so fatigue will not always be relieved by rest.
Fatigue usually occurs during the second week of radiation treatment or later. Symptoms of fatigue may increase or become more severe over the course of treatment. Fatigue usually goes away gradually after treatment has ended, but some people continue to feel tried for several weeks or months after radiation therapy.
The scalp or skin on the back may become dry, itchy, red and tender because of external beam radiation therapy. These side effects usually occur about 2–3 weeks after starting treatment and usually go away a few weeks after treatment has ended. The radiation therapy team will give instructions for skin care. Wear a hat, turban or scarf to protect the scalp from the sun and cold. Follow the radiation therapy team’s advice about using sunscreen, including on the scalp.
Thinning of the hair or hair loss (alopecia) on the scalp can occur about 2–3 weeks into radiation therapy. This side effect is due to radiation’s effect on the hair follicles. Hair loss or thinning occurs in the area where radiation is directed. If the entire brain is treated with external beam radiation therapy, hair loss occurs over the whole head.
Smaller doses of radiation usually result in temporary hair loss, but higher doses can cause permanent hair loss. When hair regrows, usually starting about 3–6 months after radiation therapy is finished, the colour or texture may be different and it may grow back thinner or in patches. It is important to be gentle with the hair when it regrows. Use a mild shampoo, a soft hairbrush and let hair dry naturally.
Somnolence syndrome is a group of symptoms that occur about 4–12 weeks after radiation is finished and can last for 2–8 weeks. Symptoms of somnolence syndrome include:
- lethargy (lack of energy)
- mild headache
Symptoms usually go away on their own after a few hours after they begin, but it may help to take a short nap. The confusion usually goes away after the person has slept.
Cerebral edema is swelling of brain tissue. It can be caused by large doses of radiation or by the tumour itself. Cerebral edema can develop quickly during treatment. It can cause increased intracranial pressure (ICP). Some of the symptoms of cerebral edema include:
- nausea and vomiting
- muscle weakness
- changes in memory and concentration
Medications called corticosteroidscorticosteroidsAny steroid hormone that acts as an anti-inflammatory by reducing swelling and lowering the body’s immune response (the immune system’s reaction to the presence of foreign substances)., such as prednisone (Deltasone) or dexamethasone (Decadron, Dexasone), are often given to reduce swelling and relieve the symptoms of cerebral edema because of radiation treatments. Corticosteroids cannot be stopped all at once, so the dose is gradually reduced over time.
Radiation therapy may cause swelling around the tumour site, which can bring on a headache. This usually occurs within the first few days of treatment.
It is important to report headaches to the radiation therapy team. They will assess what is causing this side effect and decide if they need to stop treatment temporarily, adjust medications or use pain-relieving drugs.
Seizures can sometimes occur when radiation therapy is given to the brain. Seizures are caused by abnormal electrical signals in the brain. Some people have an aura, which is an unusual feeling that warns them that they are about to have a seizure. Some seizures can be mild, while others cause more serious symptoms. Symptoms of seizures include:
- unusual smells or tastes
- visual changes or hallucinations
- twitching or jerking of the muscles or limbs
- biting the tongue
- loss of bladder control
- loss of consciousness (complete or momentary)
Anticonvulsants (anti-seizure medicines) are given to manage seizures. The healthcare team will do regular blood tests to check the level of the anticonvulsant drug in the blood. If the levels are too low, there may not be enough drug in the body to effectively control seizures. Some anticonvulsants that are used to prevent and treat seizures include:
- phenytoin (Dilantin)
- carbamazepine (Tegretol)
- valproic acid (Depakene, Epival)
For more detailed information on specific drugs, go to sources of drug information.
Nausea and vomiting are not common side effects of radiation therapy to the brain, but they may occur after 1–2 weeks of radiation therapy. Nausea and vomiting may also occur due to swelling of the brain (cerebral edema). These side effects can usually be managed with anti-nausea medication and usually go away after treatment is finished.
Earaches or difficulty hearing can happen if the ear is in the treatment area. These problems may be due to hardened earwax, irritation or damage to the middle or inner ear caused by radiation. These symptoms usually go away 1–2 weeks after radiation treatment has ended.
Hearing difficulties should be reported to the radiation therapy team. Sometimes eardrops may be prescribed. Protect the ear from exposure to the sun and cold.
Neurological changes often develop as a late side effect of radiation therapy to the brain and spinal cord. Neurological changes include:
- changes in cognitive function, including concentration and reasoning
- changes in emotions, including depression, irritability or mood swings
- short-term or long-term memory loss
- Short-term memory loss usually goes away about 2 months after radiation therapy is finished.
- speech problems
- balance and coordination problems
How radiation affects mental or emotional function is not really known. A psychologist or neurologist may assess the person and suggest ways or medications to help cope with these changes. Cognitive rehabilitation may help a person regain or cope with changes in cognitive function.
Radiation therapy can sometimes damage one or more of the 12 pairs of cranial nerves. The cranial nerves are involved in seeing, eye movement, smelling, hearing, taste and balance. They affect sensation and control the muscles of the face, tongue, throat and shoulders. Damage to cranial nerves may cause:
- vision changes
- hearing problems
- weakness of the face, tongue, neck or shoulder
The healthcare team will do a neurological examination to check nervous system function and detect changes in neurological function. These problems are more often a late effect of radiation therapy.
Hormone deficiencies (low levels of hormones) are a late side effect of radiation therapy. Radiation to the brain, especially to the area around the pituitary gland or hypothalamus, can affect the amount of hormones released into the body. Hormones that may be affected include:
- sex hormones (such as estrogen, progesterone or testosterone)
- growth hormones
- thyroid gland hormone
- adrenal gland hormones
The healthcare team may check hormone levels and prescribe medications to replace certain hormones.
Radiation necrosis (sometimes called brain necrosis) is an area of dead (necrotic) tissue that can develop at the site of a tumour after radiation therapy. Radiation necrosis can occur as early as 6 months after radiation treatment, but symptoms may not occur for 1–2 years after treatment is finished.
Symptoms of radiation necrosis are similar to increased intracranial pressure (ICP) and can include:
- drowsiness or somnolence syndrome
- memory loss (short-term or long-term)
- personality changes
Imaging tests, such as magnetic resonance imaging (MRI)magnetic resonance imaging (MRI)An imaging technique that uses a magnetic field to produce pictures of areas inside the body. A contrast medium may be injected into the body to make structures and organs show up clearly on the image. or computed tomography (CT) scancomputed tomography (CT) scanAn imaging technique that uses a computer to put a series of x-ray images together to create a 3-dimensional picture of organs, tissues, bones and blood vessels inside the body. A contrast medium may be injected to make organs and structures show up clearly on the x-ray images. , may be done to tell the difference between tumour recurrence and radiation necrosis. Sometimes a biopsy is needed to make a diagnosis. Radiation necrosis often gets worse over time.
Treatment options for radiation necrosis include:
- corticosteroids to help control symptoms and reduce ICP
- dexamethasone (Decadron, Dexasone) – most commonly used
- prednisone (Deltasone)
- surgery to remove some of the dead tissue in the brain
Leukoencephalopathy is a side effect that occurs more commonly after chemotherapy, but can also occur after radiation therapy to the brain or spinal cord. Leukoencephalopathy usually affects the white matter of the brain. The white matter contains nerve cells covered with myelin (a substance that acts like an insulator and speeds up nerve signals). With leukoencephalopathy, the myelin sheaths are damaged or destroyed (called demyelination) in the treated area and surrounding tissue.
- lethargy (lack of energy)
- ataxia (inability to coordinate movements)
- muscles spasms
- muscle weakness or paralysis
Treatment options for leukoencephalopathy include:
- anticonvulsant (anti-seizure) medications
- corticosteroids (anti-inflammatories)
- physiotherapyphysiotherapyTreatment that uses physical means, such as special exercises, activities and massage. or occupational therapy
Leukoencephalopathy is a late side effect of radiation therapy to the brain and can be permanent.
Radiation myelopathy is damage to part of the spinal cord following radiation therapy to the spine. There are 2 types of radiation myelopathy:
- Temporary radiation myelopathy is the most common type. Symptoms include electrical shock-like feelings in the skin or numbness radiating from the neck to the extremities. It usually develops about 3–4 months following treatment and resolves on its own within 3–6 months.
- Delayed radiation myelopathy is more severe than the temporary type. It usually occurs about 12–28 months after treatment, but it can take up to 4 years to appear. This type of radiation myelopathy is usually chronic (does not go away) and progressive. The symptoms begin with weakness and can progress to a complete loss of function from the area that received radiation and downward.
The risk factors for both types of radiation myelopathy include the total does and the dose per fraction of radiation.
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