Therapies with Lasers
Helen - This week, we're exploring the role that lasers play in medicine and biomedical research. Later on we'll find out how lasers and special tags can make DNA sequencing much faster, and how laser tweezers allow us to look at how cells interact on a one to one basis. But first, we're joined by Dr Martin Austwick, from the Medical Laser Centre at University College London. Martin, thanks for joining us.
Martin - Thanks very much for having me.
Helen - First of all, what sort of things are lasers being used for in medical treatments?
Martin - Well the sort of treatments we do at the National Medical Laser Centre are generally arranged arorund treating tumours or conditions which relate to cancer. That's quite a common specialty for laser therapy.
Helen - And how exactly are lasers used when it comes to treating cancers and tumours? We've got something called photodynamic therapy (PDT), haven't we? What's that all about?
Martin - Well that right. So the traditional, old fashioned approach to using lasers in medicine is use a very powerful laser used as a cutting tool which is a very clean way of excising tissue, but photodynamic therapy uses something a bit more subtle. It doesn't use a thermal laser. It is a very weak laser and what that laser does is it activates a chemical, a photochemical which under the normal circumstances is inert and don't do anything. But when you shine - mostly any kind of light, but we use lasers because they're easy to control. When you shine the laser on them, this drug activates and becomes active and it combines with oxygen in the tissue, and creates these things called reactive oxygen species which can damage the tissue around them. So it's like a very sort of microscopic level caustic burn that we're creating with this interaction of light and chemical.
Helen - And what sort cancers can this be particularly effective in treating?
Martin - It's being used around world on a whole variety of different cancers. The sort of work I've been involved with in London have been one for focal treatment of prostate cancer. It has been used in the past on the oesophagus. There's a new trial being planned on the breast, one on the pancreas. So really, there's a whole range of different options because if you've got a hollow organ like the oesophagus, it's a fairly simple matter to shine the light, put some sort of fibre into the organ and shine the light around it. If you've got a solid organ, you can actually insert a fibre via a clear needle and illuminate the solid organ from within.
Helen - Right. So it's not just a case of shining light from the outside. You can actually introduce it into the body.
Martin - Yeah.
Helen - But presumably, do you have to keep patients in the dark otherwise? Would normal light actually affect them as well?
Martin - Well that's absolutely right. Typically these drugs are administered systemically, the patient will be injected with them or they'll take them orally, and then their whole bodies will be photosensitised. So at that point, you have to keep them in [the dark]. You don't have to be excessive, but it's normally a dimly lit hospital room. And then when it comes to the time that you want to do treatment, you take them into theatre or into clinic, and you just shine the laser on the particular portion you want to treat. So on the surface, you can just shine on a bit of their skin and if it's an internal organ, you can focus the light there.
Helen - And in terms of, from the patient's point of view and in terms of how they're treated and how long it takes, and maybe the after effects as well, how does this compare with perhaps more conventional ways of treating cancers - chemotherapy and so on?
Martin - In terms of focal therapy, in terms of if you're treating an individual tumour, the big advantage of photo dynamic therapy over something like surgery or thermal laser treatment is that photodynamic therapy tends to target the living cells and not the collagen scaffolding that surrounds them. So what you tend to see is that you kill the cancer and when the tissue recovers, when it grows back, you still retain a really good cosmetic effect because the underlying scaffolding of the tissue hasn't been affected. So if you're doing something on the surface, maybe doing something for example on the head and neck, you know, you end up with a sort of treatment that doesn't leave the patient with a lot of disfigurement which can really be important.
Helen - Excellent. And lasers can also be used in another treatment which goes by the name of Photochemical Internalisation (PCI). We've got lots of good words in this story. So what's that one about? How does that differ from what we were talking about in terms of the photo dynamic therapy?
Martin - Well this is a very new treatment that we're really excited about. What this does is it works in a similar way to photodynamic therapy in that it's activating a photoactive drug. But also, you've got the additional factor of a chemotherapeutic agent and there are certain kinds of cancers that are very resistant to chemotherapeutic agents. And what this does is effectively - the chemotherapeutic agent, the chemotherapy drug will be taken up by the cells and the photo dynamic effect when you shine the laser will actually break apart the structures that are trapping and isolating the chemotherapy agents. This means that these chemotherapy agents get to the cell and can actually do what they're supposed to do which is kill the cell.
Helen - It's a way of injecting it very specifically - the chemical agent into particular cells?
Martin - Well, it's more a way of preventing resistant cells from being resistant. So it's breaking down the defences of a cell that doesn't want to be treated by chemotherapy. But it is very specific as you say.
Helen - Are you using this already or this is something that's in development?
Martin - There's a very new trial on patients which has been going for a few months now in head and neck cancers mainly, and I think that's the only one which is being carried out at the moment.
Helen - Okay, so this is something that we can look towards in the future. Well thank you Martin very much for giving us an introduction to how lasers are used in medical treatments. That's Dr. Martin Austwick from University College London.