Long term side effects of brain tumour radiotherapy

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 immediate side effects of radiotherapy to the brain. This is covered in our side effects of brain tumour radiotherapy page. A few people will have early delayed side effects. Late side effects are the rarest and will only affect a few people treated with radiotherapy to the brain.

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.

Some delayed 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 cleared up. In the meantime they take up space and cause swelling. The central nervous system is not as good at clearing up dead tissue as the rest of the body. It takes it a little longer.

The early delayed syndrome usually clears up 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 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 several 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.

Effects on brain function

Radiation can cause changes in the brain tissue. Small blood vessels may slowly become scarred and blocked. This cuts off the blood supply to areas of the brain and so some brain cells will die off. The symptoms can be mild, moderate or severe, depending on how much radiation damage there is. You may have

• Problems thinking clearly, or managing tasks you previously found easy
• Poor memory
• Confusion
• Personality changes
• Symptoms 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 late side effects of radiotherapy. CT scans or MRI scans may not help. Your doctor may suggest a PET scan or a PET-CT scan as 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.

Effects on the pituitary gland

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

• Thyroid gland
• Growth
• Sugar balance in the body
• Water balance in the body
• Fertility

So there is a possibility you could develop thyroid problems, or diabetes 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 really is rare to get another tumour caused by radiation after radiotherapy for brain tumours, but we've mentioned it because it can happen.

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.