Potential side effects of radiation therapy for childhood brain and spinal cord cancer
Side effects can occur with any type of treatment for childhood brain and spinal cord cancer, but not every child 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
- specific area or organs being treated
- total dose of radiation given
- 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 radiation therapy. Some may happen during, immediately after or a few days or weeks after radiation therapy. Most side effects go away after the child’s radiation therapy is finished. Late side effects can occur months or years later. 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 by 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. Making daily trips for radiation treatments can also be tiring for the child.
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 children continue to feel tired for several weeks or months after radiation therapy.
Nausea and vomiting are more common with radiation to the spinal cord than with radiation to the brain. This is because the stomach and intestines lie in the radiation pathway when it is given to the spine. Children may start to feel nauseous 1–3 hours after their daily treatment, about 1–2 weeks into therapy. The chance of nausea and vomiting developing depends on the amount of and how often the radiation is given.
Nausea and vomiting should be reported to the radiation therapy team. These side effects usually go away once treatment is finished.
Skin reactions occur because external beam radiation travels through the skin to reach the tumour. The skin in the radiated area may become red, dry or itchy. Most skin reactions occur within the first 2 weeks of receiving radiation treatment. They usually go away a few weeks after treatment, but some changes, such as skin darkening or scarring, can be permanent.
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. If the headache is severe, the doctor may order medications such as steroids, to reduce the swelling and relieve the pain. The headache will usually go away within a few days.
Hair loss (alopecia) or thinning can occur in any area where radiation is directed. The extent of hair loss and regrowth varies from child to child and depends on the dose of radiation.
Hair loss can begin about 2–3 weeks after radiation therapy is started. 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.
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 sydrome include:
- lethargy (lack of energy)
- mild headache
A child with somnolence syndrome will want to sleep a lot – up to 20 hours a day. Symptoms will usually go away without treatment. Not all children will develop somnolence syndrome.
Dry mouth (xerostomia) is caused by the effects of radiation on the salivary glands, which causes them to make less saliva. Dry mouth occurs within the first 2–3 weeks of radiation treatment to the back of the brain or spinal cord and can become worse over time. Dry mouth may continue for months or years and could become a long-term (chronic or permanent) problem.
It is important to follow the radiation therapy team's instructions for mouth care. They may prescribe artificial saliva and can suggest other ways to cope with a dry mouth. Regular mouth care is important for children who have dry mouth.
A sore mouth (also called stomatitis or oral mucositis) occurs because of radiation's effects on cells inside the mouth. After a week or more of radiation to the back of the brain or spinal cord, the inside of the mouth may become inflamed and painful.
Mouth sores, ulcers in the mouth and mouth infections can also develop. Thorough, regular mouth care can help to relieve a sore mouth and reduce the chance of infection. The radiation therapy team will give instructions about how often to clean and rinse the child’s mouth and what to use. Pain medications or special oral rinses may be needed to relieve pain.
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 thyroid-stimulating hormone, growth hormone and hormones that control sexual development.
- Too little thyroid-stimulating hormone can lead to hypothyroidism (a decrease in thyroid function).
- Symptoms of hypothyroidism include fatigue, hair loss, brittle nails and dry skin.
- Hypothyroidism is a late effect that may not appear for 3–4 years after the child’s radiation therapy is completed.
- It usually becomes a long-term problem. However, it is treatable with medication that replaces the natural thyroid hormone.
- If not enough growth hormone is produced, it may delay the child's normal growth and development.
- Decreased growth hormone production may not be noticeable for a few months or even years after radiation therapy.
- It usually becomes a long-term problem.
- Growth hormone injections may be given to replace the natural growth hormone.
- The production of hormones that stimulate sexual development may also be affected by radiation therapy.
- This could cause early or delayed puberty, or incomplete sexual maturation.
- The doctor will monitor the child for changes in sexual development.
A child's growth may be affected by radiation's effect on the bones of the spine. Radiation may slow or delay the growth of vertebrae, causing the child to be shorter than normal. There is little that can be done to prevent or treat this problem. Children often learn to adjust to this side effect.
Radiation therapy given to children under 3 years of age can affect the child's intellectual growth later on. It may cause memory loss, difficulty concentrating and learning difficulties at school. For this reason, every effort is made to delay radiation therapy until after the child has at least reached the age of 3.
Radiation necrosis is an area of dead (necrotic) tissue that can develop at the site of a radiated tumour. This is a rare late side effect that may appear months to many years after treatment is finished. Sometimes surgery is needed to remove the dead tissue if it is a large area.
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
It is sometimes difficult to tell the difference between radiation necrosis and tumour recurrence. Sometimes a biopsy may be needed to make a diagnosis.
A small number of children may develop a second cancer in the area that was treated by radiation therapy. This usually happens many years after treatment is finished. In fact, most second cancers do not develop until 10–20 years or more after treatment. The benefits of radiation continue to outweigh the risk of a second cancer developing. Parents should talk to their child's doctor about the level of risk.