Proton beams: better, but no magic bullet for all

Ashya King’s parents made the headlines after going to extraordinary lengths to find treatment for him at the Proton Therapy Centre in Prague.

The medical team who treated him in Southampton now confirm he wasn’t offered the therapy on the NHS because it won’t offer him any additional benefit over conventional radiotherapy.

So what is proton beam therapy? And why might it not help Ashya?

First things first. As far as doctors know at the moment, proton beams are no better at killing cancers than conventional radiotherapy.

But they probably do less damage to surrounding tissues. So, in a nutshell, proton therapy doesn’t save more lives, it just has the important benefit of minimising collateral damage.

Protons are tiny, but very heavy, particles at the centre of atoms. A therapeutic proton beam for treating cancer is made by accelerating protons to high speeds and focussing them into a beam about a millimetre wide.

Because they are heavy, behave a bit like cannonballs, releasing their energy when they land – depending on how fast you throw them.

This allows doctors to lob protons at a tumour with a high degree of accuracy doing very localised damage but with less damage to tissues behind the tumour.

By contrast, conventional radiotherapy fires X-rays at a tumour. These fly through the body damaging tissues on either side of the tumour.

In many cases the body can withstand the radiation beam. But in childhood brain tumours radiotherapy can damage highly sensitive growing brain tissue causing long term damage.

This can leave some child brain cancer survivors with lifelong disabilities.

For this reason, children with certain brain tumours are increasingly referred to proton therapy centres. Last year the NHS paid about £30 million pounds to send 23 adults and 99 children to the US for proton beam therapy.

So why isn’t Ashya King one of them? According to doctors in Southampton, and other specialists contacted by Channel 4 News, treatment of Ashya’s tumour — called a medulloblastoma — requires the entire brain to be irradiated to kill tumour cells that may have migrated away from the primary tumour site.

So while proton beam therapy might be very effective at destroying Ashya’s tumour, the conventional radiotherapy he has to receive anyway would negate any of the benefits the proton beam brings.

So, according to the experts, the expensive therapy he is about to receive in Prague will do him no harm, but may bring no long-term benefit — other than to the clinic itself which is reported to charge around £75,000 for treatment.

Follow @TomClarkeC4 on Twitter