Proton beam therapy Q&A: What does it do and how is it different to conventional radiotherapy?

Sign up for a full digest of all the best opinions of the week in our Voices Dispatches email

Sign up to our free weekly Voices newsletter

Please enter a valid email address

Please enter a valid email address

SIGN UP

I would like to be emailed about offers, events and updates from The Independent. Read our privacy notice

What is proton beam therapy?

This is a form of radiotherapy treatment for cancer involving high-energy protons, which are hydrogen atoms stripped of their electrons. Proton particles penetrate the skin and release much of their energy at the site of the tumour, destroying the capacity of cancer cells to replicate.

What is the difference with conventional radiotherapy?

Conventional “external beam” radiotherapy uses X-rays or gamma rays, which are essentially beams of photons rather than protons. The fast-moving and energetic photons work in the same way as protons by causing breaks in the DNA molecule of cancer cells, which inhibits their ability to replicate. However, the big difference between the two forms of radiotherapy is that protons release about 80 per cent of their energy directly within a tumour, whereas conventional radiotherapy releases energy continually to the healthy tissues on both sides of the tumour.

What is the advantage of proton beam therapy?

It all comes down to a part of physics called the "Bragg Peak". A phenomenon of protons is that they can be “programmed” to stop at a specific distance within the body, which is where they will release most of the energy - the Bragg Peak. Conventional radiotherapy beams made of photons continue to release energy before and after passing through the tumour, thereby damaging the healthy tissues of the body and causing more, worse side-effects.