Nuclear particle beam that kills cancerComment on this story
Proton beam therapy is an advanced form of radiotherapy that targets tumours with great precision. Kerry Whittle, 50, from Cornwall, who runs a design business, underwent the treatment for eye cancer, as he tells DIANA PILKINGTON.
MY sight has always been pretty perfect - although like most people, I needed reading glasses when I reached my 40s.
A couple of years ago I went to get a new pair and the optician spotted a dark patch on the back of my eye. She referred me to my GP, who mentioned the word ‘tumour’, but said this meant a lump, and was nothing alarming.
I was sent to Plymouth Royal Eye Infirmary, where an ophthalmologist scanned my eye and advised me to come back in a month. By this point my anxiety had gone up a notch, but everyone was reassuring me that these things are usually nothing sinister.
At my next appointment, just before Christmas 2011, I was told the tumour might have got slightly bigger and I’d need to see an eye tumour specialist.
So in January I travelled to St Paul’s Eye Unit at the Royal Liverpool and Broadgreen University Hospitals Trust. I was still optimistic - I had no symptoms and could see fine - so expected to be told my tumour was benign.
But after my eye was scanned and photographed, Bertil Damato, a consultant ocular oncologist, broke the news it was almost certainly malignant. It was next to my optic nerve, which sends visual information from the eye to the brain.
I had two options - either wait and see if the tumour grew more, or have proton beam therapy, a form of radiotherapy.
However, although this could stop the tumour growing, Professor Damato warned I’d almost certainly lose my sight within a year or two, because the radiation couldn’t avoid the optic nerve (although it takes a while for damage to appear).
It’s never great being told you have cancer, but knowing you’ll go blind, too, was a big shock.
Yet I decided to have the proton beam therapy. The next day I had a procedure at the Royal Liverpool under general anaesthetic to have three metal markers fixed around the tumour, so they could direct the radiation accurately. This involved making incisions into the muscles of my eye, rotating my eyeball, and slotting markers in.
Two weeks later, I went to the Clatterbridge Cancer Centre in Merseyside, where I had a protective mask made to keep my face still for the treatment.
In February, I returned for the first of four days of treatment (the NHS pays for patients to stay at a nearby hotel).
In the treatment room, once I was in my chair, staff fitted the mask, made me bite down on a mouthpiece, and taped back my eyelids. I found this surprisingly bearable - mainly because the staff were so kind.
Everyone left, and I was told to look into a telescope at a red dot. Although I couldn’t feel anything, I heard it humming and saw a beautiful blue glow. It took less than a minute.
After the final day, I went to the Royal Liverpool for a biopsy so they could analyse the nature of the tumour. This wasn’t nice, but I knew it was necessary.
It was wonderful to receive a letter from Professor Damato saying the tumour was not aggressive and the cancer would not have spread. The therapy had killed the cancer.
I’ll need check-ups every six months for the rest of my life. Nearly two years on - apart from a blurry area at the top of the eye I’ve had since my first treatment - my eyesight is fine, so I’m cautiously optimistic. I feel very lucky.
ANDRZEJ KACPEREK is a clinical physicist and head of proton beam therapy at the Clatterbridge Cancer Centre, Merseyside.
Proton beam therapy has been available for treating eye cancer at our centre for more than 20 years. But there are plans for more treatment centres to open in Britain in the coming years, which will allow other types of cancer to be treated in this way.
The Government has committed £250 million to open proton beam therapy centres in London and Manchester in 2018, treating certain patients, such as children with tumours in the spine or base of the skull, with larger, more powerful machines (our beam can penetrate up to 3cm, but bigger machines can go up to 30cm).
Our low-energy machine is suited to eye treatments because the beam is so sharp.
Protons (which are particles in atoms) are a form of radiation.
The therapy is tidier than conventional radiotherapy with X-ray beams because you can control the depth of the penetration - radiation stops at the tumour, minimising the damage to normal tissue. We use it for treating eye tumours where there is no other suitable option.
For Kerry, whose tumour was close to the optic nerve, the only option in the past would have been removing his eye.
With proton beam therapy, preparation is key. The patient has three to five markers - made of the metal tantalum - stitched around the base of the tumour.
This helps us see (using an X-ray) where the cancer is so we can position the patient correctly - we have to work to a precision of 0.1 to 0.2mm. We make a brass device called a collimator, which sculpts the proton beam to the shape of the tumour. The head must remain absolutely still, which is why patients wear the mask.
The radiation part takes only 30 seconds. Sometimes patients see a blue light when we use a higher dose of energy for a tumour further back in the eye.
This process kills the tumour. It becomes ‘sterile’, and stops growing, and disappears gradually. There is a very small risk of glaucoma - where pressure in the eye builds up, due to damage to the drainage ducts, affecting the optic nerve.
Another small risk is damage to eyelids - an effect of the radiation - and dry eye, if we hit the lacrimal glands, which secrete the watery component of tears. Sight loss is a possibility, but mistakes are unlikely because we can be so precise.
You could theoretically target any tumour with proton beam therapy, but it’s expensive (costing £80 million to £100 million for one facility) and is most appropriate when the tumour is next to a vital organ that other treatments would damage.
Diana Tait, vice-president in clinical oncology at the Royal College of Radiologists, says: ‘Work has been done in the U.S. using protons for prostate cancer and there have been issues about the effects of radiation on the rectum adjacent to the tumour. The jury’s still out about whether it’s better for prostate cancer than conventional radiotherapy,
‘Its use is limited to certain cancers - for others there aren’t yet studies proving it is appropriate. But the advantage to those cancers is great because you can be so specific, so it is right that we’re getting two large centres in the UK.’