Zapping cancer with lasers

11 November 2014

Interview with

Dr Ceri Brenner, Rutherford Appleton Laboratory, Oxford

Could combining lasers with a mini version of the Large Hadron Collider provide Laser experimentsAir Force Research Laboratorya treatment for cancer?

Recently, a young British boy called Ashya King, made headlines when his parents took him to Prague to receive treatment for a brain tumour using a technique called "proton beam therapy". This is available at only a small number of sites around the world because it's so specialist. It involves accelerating particles to very high energies and then firing them through the skin and into a tumour. 

Calculations are done first to work out exactly how much energy to give the particles so that when they penetrate the body they come to a standstill slap-bang in the middle of the tumour where they release their energy and destroy the surrounding cancer cells. It also means that they do minimal damage to the surrounding healthy tissue.

But these machines are very large and very specialised, which is why so few of them exist. Instead, Rutherford Appleton Laboratory researcher Ceri Brenner is developing ways to generate these same particle beams using powerful lasers, which would enable the devices to become much more compact and widely available.

Hannah Critchlow went to meet her...

Ceri -   There are two regions that plasma physicists such as myself are looking at related to cancer.  So, one of them is using the laser to drive a pulse of x-rays that could be used for imaging.  So, the imaging could be used to detect where those cancer cells are or the tumour is beneath the skin.

Secondly, that intense beam of laser light is actually so intense that it drives a microparticle accelerator, pushing forward a whole beam of particles of very, very high energies.  There's a form of radiotherapy called Hadron therapy, using very energetic particles, bombarded them through the skin.  As they crash through all the skin cells, where they slow down to absolutely zero, that's where they deposit loads of damaging energy. 

Now, that sounds a bit scary, but if we manage to tailor those particle beams that they deposit all the damaging energy within the centre of that tumour, killing the cancer cells.  But they don't deposit harmful energy to the surrounding healthy tissues.  So, it seems like the dream cancer treatment really.

Hannah -   Ceri has brought me down to a laser demo.  So, it's basically a small scale version that could be used as future technology to zap away cancerous tissue.

Ceri -   That laser is being focused down and the light intensity is so intense that it's heating the air into a plasma.  Now the plasma is very, very hot.  This could be up to a million degrees Celsius.  Heating air very, very quickly gives off a soundwave.  So, just as when lightning crashes down, we hear a thunder clap.  We're hearing a miniature thunder clap right in front of us now where the plasma is being heated by the laser.  Now, that laser plasma is the same process that we need to drive beams of particles through our Hadron therapy.

Hannah -   Once you've generated this very fast particles of beam and it's zapping through my skin tissue, how do you inform it that it's going to stop at a particular distance to discharge the energy there and just target the cancerous tissue?

Ceri -   So, that's an overlap in a radio biology and physics.  So, as a physicist, I can understand.  I can run simulations and codes and equations that will tell me that the particle with this starting energy will pass through this distance and then be stopped.  The radio biologist then come along and say, "Well actually, you're not just bombarding through random material."  The particles are travelling through cells and organic tissues.  There are other things that you have to think about in your modelling of where that particle goes.  But rightly said, that that's an extremely important part.  This technology is correct modelling of how those particles travel through the body and where they deposit that energy in that dose.  Because if we get that wrong, that's where the technology really fails, so that's crucial.

Hannah -   At the moment, how sensitive and selective is this technology?  So, if I had some cancerous tissue, how many cells would it wipe out that would be cancerous and how many neighbouring cells that might be healthy, but it also wipe out?

Ceri -   The distance between the skin outside and the tumour that's with a certain depth beneath the skin, there'll be a slight fraction of that proton or ion beam particle dose delivered to the healthy tissue, but a very slight fraction.  Actually, 80% or 90% of the energy is deposited within the tumour cells.

Hannah -   How does this technique at the moment compare to existing cancer treatment?

Ceri -   This again is an area of big debate amongst radio biologists and clinicians and doctors, and medical people.  Particle beam therapy is actually ideally suited to dealing with tumours that are in very difficult to reach areas.  So, if they're embedded within organs or perhaps they're on the edge of the eye for example or on the edge of the spinal cord or brain.  Clinicians have also advised us that proton beam therapy is very good for children with cancers because if they're treated with proton beams, the chances of having what we call secondary tumours later in life from their treatment is low when you use proton beams.  But if you use x-ray beams to treat cancers in young children, there's a chance that they develop secondary tumours from that very treatment that saved them in early childhood.

Hannah -   So, this technique has been successfully used in humans to try and zap away their cancers?

Ceri -   Yes and in fact, there are about 50 centres across the world and one in the UK that treats cancers of the eye.  But traditional systems that accelerate particles are large and costly and they don't sit well within a hospital environment.  I'd like to see these machines in every hospital around the world.  But in order to do that, we need to make the technology smaller and better suited to a clinical or hospital environment.  The laser plasma accelerators that I'm working on are better suited to that than traditional conventional accelerator machines.  So, I'm predicting this to be, I'd say, a roughly 15 to 20-year plan and that's because we're still trying to figure out the physics of how to generate these beams repetitively and with the control you would need to use in a clinical environment.  All these stages take time and a bit of patience, but have to get to see it within my career.

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