Proton Beam Therapy

Proton Beam Therapy (PBT) is a type of radiotherapy that uses beams of 'protons' (energised particles), instead of beams of X-rays ('photons'), that are used in conventional radiotherapy. The aim of both types of radiotherapy is to direct the radiation towards the tumour and destroy the tumour cells.

What is the difference between Proton Beam Therapy and conventional radiotherapy?

With conventional radiotherapy, the beams of X-rays are carefully planned to deliver most of their energy within the tumour, whilst avoiding as much healthy brain tissue as possible. However, the X-rays do also release some of their energy before they reach the tumour, and continue to release some after they have passed through the tumour and continue on through the brain to exit on the other side of the head. This causes some damage to the normal, healthy cells in the path of the radiotherapy, but normal brain cells are more able to repair themselves than tumour cells. This initial damage to the normal cells, however, can cause side-effects in the short-term. Some of the damage may be unrepairable, leading to long-term effects.


Conventional radiotherapy beam

Similarly, in PBT the beams of protons are carefully planned to target most of their energy within the tumour.

However, by altering the beam energy, the beam can be designed so that the protons stop and release most of their energy accurately at a particular depth in the brain i.e. where the tumour is situated.

This means that although some of the energy will be released before they reach the tumour, the main radiation dose can be given to the tumour and very little is released the other side of the tumour. (The beam is usually set up to travel a little way past the tumour to make sure it gets any tumour cells beyond the edge of the tumour that can't be seen.)

This means that fewer healthy cells nearby receive a dose of radiation. This is particularly important in children, whose brains are still developing.


Proton Beam Therapy beam

Why isn't everyone given Proton Beam Therapy?

Whether your child/you can have PBT depends on many factors, including:

  • Brain tumour type
    PBT works best for smaller tumours, where the edges are clearly defined. There is a nationally approved list of tumour types that are suitable for referral.
  • Timing of when the radiotherapy needs to be given
    PBT for brain tumours is not currently available in the UK. Referral abroad may crucially delay giving radiotherapy to your child/you
  • Timing of when the radiotherapy needs to be given in relation to other treatments
    PBT needs to link seamlessly with surgery and chemotherapy. Delays, can lead to less intensive therapy and less tumour control. As a result, if your child/you has a diagnosis on the approved list, PBT may still not be the best radiotherapy option.

It is important to appreciate that Proton Beam Therapy is not suitable for everyone.

It is also important to realise that:

  • PBT is a relatively new therapy that is usually used for rare types of tumours. This means there is little evidence about its effectiveness compared to conventional radiotherapy, particularly about long-term side-effects.
  • The way it works when it reaches the tumour is much the same as conventional radiotherapy.
  • The quicker 'stopping' of the radiation in PBT means getting the target right is very important.
  • It requires extra training and skill to work out the required depth and dosage of PBT.
  • It is harder to check what is actually being treated during PBT treatment - conventional radiotherapy can use imaging to check the accuracy of the treatment area, which is important when near to critical structures, e.g. spinal cord or optic nerve.
  • People who travel to receive PBT often respond well, but they are 'optimally chosen' who are more likely to do well.

What happens if Proton Beam Therapy is suitable?

If the strict set of criteria for referral are met, your oncologist will refer you to one of the approved PBT treatment centres in the USA or Europe (Switzerland). Children are normally treated in the USA.

The referral process has many stages, which can take nearly three months (11 weeks) to complete - from when your consultant first suggests this could be appropriate treatment to receiving the first PBT.

At any stage, treatment can be refused on the grounds of PBT not being the best option for your child/you.

The NHS will cover the cost of PBT at these approved treatment centres. It will also fund economy travel and approved accommodation for the patient, plus one to two carers/parents accompanying them. The NHS will NOT fund any meals or refreshments, nor any upgrades to travel or accommodation.

You will need to sort out your own travel insurance and appropriate visas. (If you are going to the US, your travel insurance will be refunded).

(There are slight variations to the process of NHS funding according to which UK nation you live in.)

If you need help with associated essential costs not covered by the NHS, contact our Support & Info Line about sources of grants and other financial help that may be available. Alternatively, your local neuro-oncology centre may have access to charitable funding.

(There are other (private) centres overseas. However, these can be expensive, may not have sufficiently trained staff and often don't offer other treatments, such as chemotherapy, which may be needed alongside the PBT. This could influence the overall effectiveness of the treatment.)

Two Proton Beam Therapy centres for treating brain tumours are planned in the UK (Manchester and London) for 2018/19.

How is Proton Beam Therapy given?

The procedure for giving PBT is very similar to conventional radiotherapy.

In preparation:

There will be several planning appointments at the treatment centre before you/your child starts PBT. These include:

  • Scans to plan the treatment and programme the machine accurately.
  • A radiotherapy mask will be custom-made to keep your child's/ your head still and in position during the PBT sessions.
  • The chance to discuss the treatment, what to expect and any possible side-effects.

The Proton Beam Therapy procedure:

  • Your child (or you) will lie on a treatment couch, and the mask will be placed over their/your face and attached to the couch. You will be positioned correctly.
  • Before the PBT begins, the radiotherapy team will leave the room, but they can still see and hear your child or you.
  • The PBT machine will direct the protons towards the tumour.
  • After treatment, the team will re-enter the room and help take off the mask.

You will then usually be able to go straight home.

The treatment generally only lasts one minute, but with the positioning and adjustments, the session is likely to be about 20 minutes.

It is usually given daily (Monday to Friday) for up to 5-7 weeks. This depends on your child's/your tumour type and grade.

You will need to be away from home for at least 8 – 10 weeks.

What are the side-effects?

These are likely to be fewer than with conventional radiotherapy, but how your child/you feel will depend on the size of the dose of PBT you had and whether you are having any other treatment, such as chemotherapy.

The following short-term effects are common:

  • Fatigue
  • Redness that resembles sunburn
    (in the area where the proton beam was directed)
  • Hair loss

These are usually temporary and often disappear after treatment has finished.

You will not be radio-active after treatment – it is safe to be around others, including children.

Longer-term effects after PBT in children can include:

  • Hearing loss, which can be severe
  • Cognitive impairment, particularly thinking speed and understanding language
  • Changes in hormone levels, particularly growth hormone

(These effects are also possible with conventional radiotherapy.)

Ask your health team about how to ease any side-effects you or your child experience.

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