Potential side effects from radiation for brain tumours

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An in-depth discussion of the possible side effects of radiation for children with brain tumours.

Key points

  • The effects that your child experiences from radiation therapy depend on their age, the area of the brain being treated and the amount of radiation.
  • Side effects from radiation therapy include fatigue, hair loss, nausea or vomiting, headaches, and skin problems.
  • Some effects may be experienced during treatment, while other effects may happen in the weeks, months or years following treatment.

Radiation therapy destroys cancer/tumour cells but may also affect normal cells within the area being treated. Fortunately, most normal cells are less sensitive to the effects of radiation, and they can recover easily from radiation effects than cancer/tumour cells.

Many children who have radiation do not experience any side effects. Whether your child will experience side effects depends on several things including:

  • the area of the brain being treated
  • the amount of radiation prescribed
  • the size of the area being treated

The radiation oncologist will discuss with you in detail the expected short-term and long-term side effects specific to your child’s treatment at the initial visit.

Potential side effects during treatment

Fatigue during radiation therapy

During radiation therapy, your child’s body will use more energy than it normally does. Your child may feel very tired. Other factors can add to the fatigue as well, such as the stress of coping with a serious illness and the trips made for treatment. Other treatments such as surgery or chemotherapy may also have an effect. Poor appetite and nutrition, lack of sleep, pain, nausea, vomiting, lack of physical activity, and low blood cell counts can also make fatigue worse.

What you can do:

  • Encourage your child to eat a well-balanced diet.
  • Offer lots of fluids.
  • Space out your child’s activities if possible. Allow times for rest, relaxation, and naps if necessary.
  • Stay active, but do not overdo it.

Hair loss

Hair loss is a common side effect of some chemotherapy drugs. Hair roots are also sensitive to radiation. Hair in the treatment area may fall out. In most cases the hair will regrow within 2 or 3 months. Sometimes, the hair that grows back may be a different colour or texture. However, higher doses of radiation may cause permanent hair loss.

What you can do:

  • Your child may wish to wear a wig. If you get a prescription, some health insurance might cover part or all of the cost.
  • If your child doesn’t want a wig, they may pick out several hats or scarves before hair loss begins.
  • Use a mild shampoo and soft hairbrush.
  • Use a sunscreen, sun block, hat, or scarf to protect the scalp from the sun if they lost hair on their head. Discuss with your radiation treatment team before using any creams on the scalp during treatment.

Lack of appetite, nausea or vomiting

At times, the radiation may cause loss of appetite, nausea and/or vomiting. If your child feels sick or is throwing up, the doctor may prescribe anti-nausea drugs. One example of an anti-nausea drug is ondansetron. Your child may need more than one kind of anti-nausea drug.

What you can do:

  • Give your child small meals or healthy snacks throughout the day.
  • Serve crackers, toast, yogurt, pretzels, oatmeal, skinless chicken (baked or broiled), soft and bland fruits and vegetables. Popsicles or ice chips may help with the nausea.
  • Try giving your child water, unsweetened fruit juice, or flat ginger ale between meals. Tell your child to drink slowly with small sips.
  • Some foods, such as meats or chicken, may be easier to keep down if they are served cold.
  • Try to maintain a balanced, healthy diet.

Skin problems

Some children will experience skin reactions in the area that had treatment. After 2 or 3 weeks of treatment, these areas might become red or brown, warm, and sensitive. In some situations, the skin may peel or, rarely, may blister like a sunburn.

The following are guidelines for the care of skin in the treated area:

  • Gently cleanse the treated area with mild soap and lukewarm water. Pat the skin dry with a soft towel.
  • If the skin becomes dry and itchy, do not scratch the area. If itchiness becomes a problem, the radiation oncologist will prescribe a cream to relieve it.
  • All treated areas should be protected from irritation due to rubbing and pressure. Avoid tight fitting clothes and harsh fabrics.
  • Do not apply tape to the skin within the treated area.
  • Do not expose the treated area to extremes of hot and cold, such as a hot bath or shower. Keep treated skin protected from the sun by using a large-brimmed hat or clothes that cover the body.
  • You may use mild water-based creams for dryness in the area of treatment.

The skin problems will get better gradually within 2 to 6 weeks after finishing treatment. Once the treatment is complete, creams or lotions may also be used. With time, the treated skin may become darker and appear tanned. Gradually it will return to normal. Remember to avoid exposing this area to excess sun.


Radiation may cause some swelling (edema) around the tumour site which may cause your child to experience some degree of headache and/or nausea after the first few treatments. These symptoms do not always occur, but when they do, they usually settle within a few days. If your child is experiencing headaches, let the radiation team know and they may recommend observation or medication.

Potential side effects in the months following treatment

Fatigue after radiation therapy (somnolence syndrome)

In the 2 to 8 weeks after radiation therapy has ended, your child may start to have symptoms such as feeling drowsy, tired, irritable, or sleeping for hours more than they normally do. They may also have some mild headaches and a loss of appetite.

These symptoms may be part of a condition called somnolence syndrome. Some parents find this upsetting, but the symptoms will usually go away in about 4 to 6 weeks. The symptoms are believed to be caused by damage to the covering of the nerve cells and recovery after radiation.

Stay in touch with your treatment team if you are worried about your child’s symptoms. If the symptoms are severe, dexamethasone may be given to help.

Potential side effects in the years following treatment

The combination of surgery, radiation therapy, and chemotherapy over the last several decades has significantly improved the cure rate in children with brain tumours. Many children still have significant development ahead of them at the time of treatment, so radiation therapy can be associated with some additional possible late effects. Many of these radiation late effects are not only related to the radiation therapy itself but are often also related to the brain tumour and the effects of surgery and chemotherapy. Some of the long-term side effects are described below.

Cognitive effects

Radiation therapy to the brain in a young child can be associated with cognitive effects that can impact learning and success at school over the months and years following radiation.

The factors that are associated with a greater degree of impairment are:

  • younger age at treatment
  • location of the tumour in the child’s brain
  • larger area of brain receiving treatment
  • higher radiation dose

Radiation is always considered very carefully for children younger than 3 years old. At this age, the connections of the brain are developing very rapidly and may be impaired by the radiation. An endocrine and neuropsychological assessment may be needed.

Growth changes

Radiation therapy to any part of the body can be associated with growth effects in that particular area. The factors that predict a greater impact on growth are:

  • the amount of tissue being treated
  • younger age at treatment
  • the specific area being treated

More specifically for brain tumour patients requiring cranio-spinal irradiation, radiation to the spine can impair growth by a direct radiation effect on the bones of the spine.

Hormonal function

Radiation of the brain can affect hormonal function. The 4 main hormonal systems are all centrally controlled by the hypothalamus/pituitary complex in the brain. Radiation to the pituitary or hypothalamic area may sometimes be associated with a decrease in hormone production from a few months to a few years later.

The most commonly affected hormones are growth hormone, which is very important for growth in children, and thyroid hormone. Both of these hormones can be replaced by medication. The hormones that are associated with sexual development and stress are more resistant to radiation and are less commonly affected.

Risk of secondary cancers

Radiation to the brain can be associated with the development of new tumours in a small number of patients many years after successful treatment of a brain tumour. However, this risk is very low, and the benefit associated with radiation in terms of curing the current disease significantly outweighs the risk of a second cancer in the following decades.

The radiation team will let you know which of these effects apply to your child depending on their age, tumour type, treatment plan, tumour location and other factors.

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Last updated: January 10th 2022