Mini-lecture: New laser treatment for tumours (UCL)


Uploaded by UCLTV on 06.05.2010

Transcript:
My name's Dr Martin Austwick
and I'm a laser physicist at the National Medical Laser Centre,
which is part of UCL, but we have very strong links with University College Hospital
and the Royal Free Hospital up in Hamstead.
The Laser Centre
as you might guess, started out to research
lasers in medicine.
But in recent years it's sort of broadened out to cover
the use of light and other minimally invasive techniques for detection and treatment of disease.
And one of the things we're pretty well know for is photodynamic therapy,
which is this technique which has three components. It uses light,
it uses a particular kind of drug
and it uses oxygen in the body
together to create a therapeutic effect.
I always think of this as a sort of
technique which uses three boring things to
get something more interesting
because on their own each of these techniques or elements doesn't do anything.
So the light itself
is- typically we use a laser.
But it's not very powerful.
It's not the sort of intense beam that would give you a burn
if you shone it on yourself.
So on its own it doesn't really do very much.
The next
component we use is the drug.
We use drugs called photosensitisers.
And these are drugs which on their own, they don't do much at all. If you took them,
they would just pass through your body and not have an effect.
But when you shine a light on them, for example the laser light we use,
they get activated,
and they become a more reactive form of themselves, and they can start to interact with the chemicals around them.
Now this sounds looks like slightly magical and science fiction-y.
But actually these chemicals are really, really common.
If you look at plants,
chlorophyll
does exactly that in the process of photosynthesis. It takes energy from the sun--
it takes light from the sun,
and it converts it into
a chain of chemical reactions, which moves energy and chemicals around the plants.
So
we take these photosensitive chemicals, photosensitiser chemicals,
that become activated by the light
and then in the body, you tend to have a lot of oxygen around the place.
Almost throughout the entire body, you'll find oxygen
because cells need it to survive and to respire
and under normal circumstances
this oxygen doesn't do very much. It just helps
the body keep on going.
It doesn't have any therapeutic or dramatic effect.
But when you combine it with this activated chemical,
it can produce reactive oxygen
'species', we call them, so just different types of reactive oxygen.
And these reactive oxygen
species, they will
move around from the site that they were created and start to bash
into cells and living structures
and have a chemical reaction and start to damage them.
So it's a little bit like having a very, very small, microscopic chemical burn,
where only we're producing the chemical burn at the site
by this photodynamic effect.
You might very reasonably say, well, why would you want to do this?
Why are you trying to burn tissue? Well, obviously, with normal tissue, there's no reason to do that.
But if you've got issue
which is unhealthy, for example, you've got
a benign tumour or cancer or something that might lead to cancer,
and you want to kill it before it gets to that stage,
this is the sort of technique that you want to use.
So the way that this works in practice
is, you bring your patient in.
This is our patient.
The patient is full of oxygen because they're just naturally full of oxygen from breathing
and you give them a photosensitiser.
And what you generally do is you give it to them systemically, so you inject it
or they take it by mouth.
And so, just a little bit of chemical
goes through their whole body.
And as their heart bumps the blood around their body, this chemical
gets forced around the body and goes around their organs and in their skin,
all around the different parts of the body.
And at this point, the patient is going to have
this photosensitiser
throughout the body
and so any part
of the body that you shine a light on,
if it's an intense enough light,
will cause this chemical burn.
So if this patient went out on a bright sunny day like this,
they'd get a nasty skin burn, so you have to keep them out of the light. In this case,
we're going to cover him up.
But in general,
you don't need to put a handkerchief over a patient's head. You can keep them in a dimly hospital room
and the light levels in a dimly lit room are fine.
So at this point you have to leave the patient for a while. You have to make sure the drug
is where you want it to be
and of the right concentration for the treatment.
So you leave them for a little while,
depending on the drug,
and you come back and hopefully the drug has got everywhere.
So then you take them into clinic. And let's say this chap has got a,
something on his back that you want to treat.
And you take your laser
and you just shine it on the little
region that you want to treat.
So if we shine it here,
hopefully you can see
that there's a little bit of a region of treatment
around that part of his back.
And that means just that part
of the patient will
will be radiated and will have that chemical burn
and if there's a lesion there, it will get damaged and shrunk down and killed off, hopefully.
So there are two very obvious advantages of this treatment. The first one is that it's
very targeted.
If you know what you want treat, you can just focus in and treat that.
And the other one is to do with the way that photodynamic therapy
tends to kill living cells only.
Now, I'm a physicist, so my sort of primitive understanding
of tissue physiology is that
what you have is a sort of matrix of proteins which are somewhat inert,
things like collagen, which give
the organs of your tissues structure and shape.
And then in that matrix
between the little gaps are little living cells, which actually respire and do the business of living.
Now, traditional treatments like old-fashioned laser treatments were using
an intense beam of laser light
or surgery were using a cutting devise
kind breaking these matrices apart, breaking apart the scaffolding
of the tissue.
And that means when they heal up afterwards,
you get scarring and disfigurement and these sorts of issues.
With photodynamic therapy, what tends to happen is you're targeting the living cells
And not the matrix and the matrix tends to stay intact,
which means that when you kill off your naughty cells, whatever they may be,
they die off sometime later.
Those gaps will be repopulated by healthy, normal cells. But the structure,
the matrix will have been kept intact.
So you won't get the same degree of damage or disfigurement to the organ.
And if it's something visible, if it's something
on the skin or the face, for example, that's really, really important for the patient.
So
photodynamic therapy, it's applicable in a whole range of different organs,
and we're investigating that as we speak.
It's already been proven effective in a number of those organs.
And in many cases it has this very, very positive cosmetic effect after treatment.
So it's something we're really excited about.