What is proton beam therapy?
Proton beam therapy is a type of radiotherapy. Conventional radiotherapy usually uses high-energy x-rays (also called photons) to destroy cancer cells, but proton beam therapy uses small parts of atoms called protons instead. Protons, however, can more precisely target a tumour than x-rays can. The protons release their energy at the site of the tumour.
Proton therapy is currently unavailable in the United Kingdom. The Department of Health will pay for proton treatment of carefully selected patients at hospitals in other countries, usually Switzerland and the USA, if this is felt to be the best treatment for them. Most children who need proton beam therapy are treated in the USA.
Although the evidence and follow-up data for proton beam therapy is still limited, the data gathered so far suggests it has good outcomes for certain forms of cancer, including complicated childhood cancers and may cause less long-term side effects. There is no difference in the biological effectiveness of protons versus photons in terms of the damage they cause to cancer cells, but they deliver the dose slightly differently.
How proton beam therapy works
Like other forms of radiotherapy, the aim of proton beam therapy is to destroy the DNA in cancer cells. DNA is the instruction code that tells a cell what kind of cell it is and what job it has to do. Destroying it kills the cancer cells and shrinks the tumour.
With proton therapy the energy hits mainly the tumour site and, unlike photons, does not deliver a dose beyond the tumour.
This means the dose of radiation maps onto the tumour better and there is less damage to healthy tissue. Because of this, doctors may recommend proton therapy if you have a tumour that is close to delicate parts of the body, such as the brain or spinal cord.
Only a few young people qualify for this treatment, which is especially useful for rare cancers affecting the base of the skull and the spine.
How is proton beam therapy given?
People having proton beam therapy are treated as outpatients. Treatments are usually given daily from Monday to Friday with weekends off. The proton treatment course usually lasts about six to seven weeks in total.
Because proton beam therapy is so carefully targeted, it is very important that people having it stay still during the treatment. If you are having proton beam therapy on your head or neck, you may have a special mask made for you that keeps your head still.
Proton beam therapy is painless and treatments usually last up to about one hour in total.