Cancer treatment: Is proton beam therapy suitable for everybody?

IT’S UNDERSTANDABLE that most people diagnosed with cancer will want to ensure they’re getting the best treatment available.

In 2014, the story of five-year-old brain tumour patient Ashya King put proton beam therapy (PBT) in the spotlight and sparked an international manhunt after his parents took him out of a UK hospital where he was being treated in a bid to get PBT for their son abroad.

Ashya finally had the treatment in Prague, and last year his father Brett said his son was cancer-free.

WHAT IS PBT?

Most conventional radiotherapy treatments use X-rays (photons) to damage cancer cells so they can’t multiply and will die.

But X-rays don’t discriminate between cancerous and healthy tissue, and can carry on through the tumour and destroy normal cells near it, causing serious side-effects.

This is particularly harmful for children, as they’re still developing and are more susceptible to the effects of radiation.

They’re also slightly more at risk of developing another cancer later in life, due to early radiation exposure.

Zapping tumours with protons — positively-charged particles found in the centre of atoms — offers the chance to avoid such risks, as they can damage cancer cells in the same way as conventional radiotherapy, but stop once they hit their target.

This means there’s less chance of damaging surrounding healthy tissues, reducing side-effects.

As Dr Jiri Kubes, medical director at the Proton Therapy Center in Prague, puts it: “Proton therapy maximises curability while significantly minimising the risk of possible side-effects, ultimately preserving patients’ quality of life.”

IS IT BETTER?

A 2015 US study found PBT caused fewer side-effects in children than conventional radiotherapy.

Researchers from Massachusetts General Hospital studied 59 patients aged between three and 21 and found after five years, the children’s survival rate was similar to that of patients treated with conventional radiotherapy, but with fewer side-effects to the heart and lungs.

“It’s critical to stress that for most patients right now, there’s no strong evidence that proton beam radiotherapy is ‘better’ at curing cancer, or improving a patient’s chances of survival, than conventional X-ray radiotherapy,” says Oncologist Dr Adrian Crellin, NHS England’s clinical lead on PBT.

He says more research is needed.

WHO CAN HAVE PBT?

PBT isn’t available in Ireland and trials aren’t taking place.

Clatterbridge Cancer Centre in the Wirral offers low-energy PBT for rare eye cancers in the UK.

As only a small number of cancer specialists have practical experience with PBT, Dr Kubes thinks they may be reluctant to give information to patients about the treatment.

“The approach to PBT is changing though internationally — several centres are presently under construction, and I believe the UK could become a leading country in the proton therapy field,” he adds.

Cancer researchers point out PBT isn’t a ‘magic bullet’ and won’t suit all.

Although it may have fewer side-effects, it still carries some risks and uncertainties.