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Long term side effects of radiotherapy

Read out about the possible long term side effects of radiotherapy for a brain tumour. 

Long term side effects of radiotherapy won't happen to everyone. For most people, the benefits of the radiotherapy treatment far outweigh the risk.

Some people may have late side effects that can start months or years after treatment with radiotherapy. Unfortunately, there is no way that doctors can tell beforehand who will have long term effects and who won't.

Side effects in the first few months

Some side effects can start from a few weeks to a few months after finishing your treatment. This collection of symptoms is called somnolence syndrome or early delayed syndrome. It is more common in children, but can also happen in adults. You might have:

  • poor appetite
  • sleepiness
  • lack of energy
  • worsening of your old symptoms

These side effects happen for 2 reasons. The fatty covering of the nerves can be damaged by radiation and this takes a few weeks or months to repair. The radiation kills tumour cells but also damages some healthy brain cells. These dead cells must be removed by the body's repair systems. In the meantime they take up space and cause swelling.  

Somnolence syndrome usually gets better in about 6 weeks. 

In more severe cases, it can take a few months. Often you won't need any treatment. But you may have to take steroids to control the swelling caused by the dead tumour cells.

Late side effects in adults

Late side effects only affect a small number of adults. They are less common than in the past because radiotherapy planning is very precise these days. Only the area of the tumour receives high doses of radiation.

When late effects do happen, they can come on from a few months, to many years after treatment has finished. Unfortunately, this can be permanent.

Effects on brain function

Radiation can cause changes in the brain tissue. Small blood vessels may slowly become scarred and blocked, reducing the blood supply to some areas of the brain. The symptoms can be mild, moderate or severe, depending on how much radiation damage there is.

You might have:

  • problems thinking clearly
  • difficulty managing tasks you previously found easy
  • poor memory
  • confusion
  • personality changes
  • headaches similar to migraines that come and go (called SMART attacks)

You might also have symptoms similar to those you had from your original tumour. Your doctor may suggest a PET-CT scan because this can show up the difference between active cells (tumour cells) and scar tissue or radiation damage.

Treatment to reduce these side effects 
You might have treatment with steroids or surgery to reduce these side effects. You are more likely to have steroids if your side effects are mild. You might need high dose steroids for long periods of time.

Some people need surgery to remove an area of dead tissue. This is most likely after treatment with radiosurgery. Fewer than 1 in 20 people who have late effects from radiosurgery, need an operation to remove this dead tissue.

Hormone level changes

You might develop hormone imbalances in the future if your pituitary gland is near your treatment area.

Diagram showing the pineal and pituitary glands

For example, there is a possibility you could develop thyroid problems, or low levels of steroids in the future.

Your doctor will check for this and you can take replacement hormones to correct any imbalances.

A second brain tumour

In very rare cases, you may develop another brain tumour many years after you were first treated. This is because, although radiation kills cancer cells, it is also a risk factor for developing them. 

Unfortunately, tumours caused by previous radiotherapy tend not to respond very well to treatment. The tumours might be high grade and grow more quickly.

Talk to your treatment team if you are worried about developing a second cancer in the future.

Late effects in children

Unfortunately, long term side effects for children are more common. This is because the nervous system is still developing in children when they are treated. Because it is still developing, the nervous system is more likely to be damaged by radiation.

If possible, radiotherapy is avoided in very young children for this reason. Children might have other treatments instead. Or other treatments to control the growth of the brain tumour until they are older. 

Last reviewed: 
22 Oct 2015
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