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February 28, 2019

Understanding Proton Therapy

Understanding Proton Therapy

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Proton therapy is a new and innovative type of radiotherapy that can limit the damage to healthy tissue

Whilst conventional radiotherapy is normally safe and effective in killing cancer cells, like all treatments, it has a list of side effects. Most concerning is that radiotherapy damages the healthy cells surrounding the cancerous area being treated. Proton therapy—also known as proton beam therapy—is a type of radiotherapy that combats this. Unlike conventional radiotherapy, proton therapy uses beams of accelerated protons (sub-atomic particles) to kill the cancer cells. This beam stops once it targets the cancerous cells, resulting in less damage to the surrounding tissue. If the cancer is in an area of the body where subsequent damage would be serious—such as complex child cancers of the brain, spinal cord or optic nerve—proton therapy may be recommended.

What to expect

Treatment planning for proton therapy is similar to conventional radiation procedures. The treatment is an external beam of positively charged particles that are sped up using a machine called a synchrotron or cyclotron. The protons are directed to the intended area and deposit a dose of radiation into the cancerous tumour before stopping. 

Usually, the treatment lasts around 15 to 30 minutes with the patient spending up to one hour a day in the treatment room. The patient must be in the same position for each day of treatment and may be fitted with an immobilisation device. For example, a facemask or bite-block may be used. Fiducials may also be inserted to guarantee that the procedure is precisely located every time. This type of therapy is painless, patients have not reported any discomfort during their sessions.

The number of treatment sittings also depends on the type and stage of cancer. Treatment does not require an overnight stay and doctors may use proton therapy alone or combine it with other treatments. After the therapy, patients may experience side effects.

Is it as good?

According to the NHS, it is still unclear whether proton therapy is as good at destroying cancerous tissue as conventional radiotherapy. The therapy is considerably new to the UK and is recommended for rare, specific types of cancer, limiting the systematic evidence available. People who have received proton therapy in other countries have reacted well—figures and research seem very promising. 

Proton therapy may deliver up to 60 percent less radiation to surrounding healthy tissue. Other benefits may include the possible allowance of a higher, controlled dose of radiation that can increase the chances of all cancer cells being destroyed. There are also some studies that suggest patients present with fewer side effects after undergoing proton therapy compared with conventional radiotherapy treatment. In a study funded by the US National Cancer Institute and Massachusetts General Hospital, 59 children with medulloblastomas (brain tumours) were treated with proton therapy. The results concluded that both hearing loss and cognitive impairment effects were both slightly less than conventional radiotherapy statistics. The NHS has analysed these results on their website, stating that they 'seem positive’.

Proton Therapy in the UK

Currently, there is a low energy proton machine at the NHS Clatterbridge Cancer Centre in Merseyside, used to treat some specific eye cancers. Around £250 million has also been committed for the NHS to build a proton beam centre in both London and Manchester—these centres are expected to open in the near future. 

Meanwhile, there have been around 400 optimal patients, mostly children, who have been sent abroad for centrally funded treatment since 2008. On average, these patients were abroad for nine weeks. Some overseas clinics strongly recommend proton therapy as a treatment to parents who have sick children. This could be problematic as proton beam therapy is more costly than conventional radiotherapy.

Important

Side effects of conventional radiotherapy and proton therapy can occur during treatment, directly after treatment or months to years after treatment 

Source: NHS

Did you know?

Cancer Research UK estimates that only 1 in 100 people with cancer would be suitable for proton beam therapy 

Source: NHS

1,500 

cancer patients are offered proton therapy per year at the Christie NHS Foundation Trust in Manchester and University College London Hospitals NHS Foundation Trust 

Source: Cancer Research UK

This article was originally published in Live to 100 with Dr Hilary Jones. Read the digitial edition, here.