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For most people, the benefits of radiotherapy treatment to the brain far outweigh the risk. But some people may have late side effects that start months or years after the radiotherapy treatment.

Side effects in the months after treatment

Some side effects can start from a few weeks to a few months after finishing treatment. You may have poor appetite, sleepiness, lack of energy or a worsening of your old symptoms. You may hear this called early delayed syndrome. It usually gets better in about 6 weeks. In more severe cases, it can take a few months. Often you won't need treatment but some people need to take steroids to control the side effects.

Late side effects in adults

Late side effects only affect a small number of adults. They can come on from a few months to many years after treatment. The late side effects are usually permanent and may also slowly get worse over a long period of time. They are due to changes in the brain tissue caused by radiation.

Changes in brain function

You may 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), or symptoms similar to those you had from your original tumour. You may need to take steroids to reduce the side effects. It can be difficult for you and your doctor to tell whether you have symptoms from your tumour coming back or from the late side effects of radiotherapy. Your doctor may suggest a PET-CT scan to show up the difference between active cells (tumour cells) and scar tissue or radiation damage.

Hormone level changes

If your pituitary gland is near your treatment area, you could develop hormone imbalances in the future. You could develop thyroid problems, or low levels of steroids. You can take replacement hormones to correct any imbalances.

A second brain tumour

Some people develop another brain tumour many years after treatment but this is very rare.

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. We have detailed information about long term effects in children in the living with brain tumours section.

 

CR PDF Icon You can view and print the quick guides for all the pages in the Treating brain tumours section.

 

 

Who gets long term effects

Treatment for a brain tumour can have long term effects. These will not happen to everyone. For most people, the benefits of the radiotherapy treatment far outweigh the risk. But 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.

Nearly everyone will have some side effects during radiotherapy treatment to the brain and for a few weeks afterwards. This is covered in our side effects of brain tumour radiotherapy page. A few people will have side effects that start some weeks or months after the treatment ends. Some side effects may start some months or years later but are very rare and will only affect a few people.

If you have had radiotherapy to any other part of your body, you will not be at risk of late side effects to the brain. Radiotherapy only affects the area of the body that was treated.

 

Side effects in the months after treatment

Some side effects can start from a few weeks to a few months after finishing your treatment. You may have

  • Poor appetite
  • Sleepiness
  • Lack of energy
  • A 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. You may hear this called early delayed syndrome. It 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. If you do develop late effects, they can come on from a few months to many years after you were first treated. Unfortunately, these late side effects are usually permanent. They may also slowly get worse over a long period of time.

The effects may include

 

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 may 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)
  • Symptoms similar to those you had from your original tumour

Because they can be similar, it can be difficult for you and your doctor to tell whether you have symptoms from your tumour coming back or from the late side effects of radiotherapy. CT scans or MRI scans may not help. 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.

If you have mild late effects, you are most likely to have treatment with steroids. Some people need surgery to remove an area of dead tissue. This is most likely after treatment with radiosurgery. About 1 in 20 people (5%) who have late effects from radiosurgery need an operation to remove this dead tissue.

 

Hormone level changes

If your pituitary gland is near your treatment area, you could develop hormone imbalances in the future. The pituitary gland controls your

  • Thyroid gland
  • Steroid levels
  • Growth
  • Water balance in the body
  • Ability to have children (fertility)

So there is a possibility you could develop thyroid problems, or low levels of steroids in the future. 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 are often malignant and tend not to respond very well to treatment. It is very rare to get another tumour caused by radiation after radiotherapy for brain tumours but we've mentioned it here because it can happen.

 

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. There is detailed information about long term effects in children in the living with brain tumours section.

 

More information about brain radiotherapy side effects

We have general information about the side effects of brain tumour radiotherapy in the radiotherapy section. There is information about side effects during and after brain radiotherapy in this section.

You are also welcome to contact the Cancer Research UK nurses on freephone 0808 800 4040. Lines are open from 9am to 5pm, Monday to Friday.

You can contact one of the brain tumour organisations or look at our brain tumour reading list. If you want to find people to share experiences with online, you could use Cancer Chat, our online forum.

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Updated: 30 December 2013