Zooming in on radiotherapy

How does radiotherapy work, and where is it going in the future?
02 May 2017

Interview with 

Alison Tree, Royal Marsden Hospital, Uwe Oelfke, The Institute of Cancer Research


 Shows the beam's eye view of the radiotherapy portal.


One cancer treatment in the arsenal of doctors is radiotherapy. It may not be as well known as chemotherapy or the expensive cancer drugs that hit the headlines, but radiotherapy is the cornerstone of many successful cures.  Kat Arney caught up with Uwe Oelfke, and before him Alison Tree, a consultant clinical oncologist at the Royal Marsden Hospital, who’s a specialist in treating prostate cancer, to find out more about radiotherapy.

Alison - Radiotherapy is high energy X ray treatment that we use to target cancers to kill off the bad cells, the cells that cause cancer. It works because the cancer cells turnover very quickly - that’s part of what makes it cancerous. Whereas your normal tissue turnover very slowly so they’ve got plenty of time to repair any damage caused by the radiotherapy. Whereas the cancer cells get killed off and, hopefully, the cancer is then cured.

Kat - What sort of cancers can be treated with radiotherapy?

Alison - Most sorts of cancers can be treated with radiotherapy and, actually, radiotherapy is involved in about 40% of cancer cures. So it’s a very cost effect and effective treatment for cancer. Most cancers, for example, prostate cancer; the largest proportion of prostate cancer is cured by radiotherapy rather than surgery.

Kat - What sort of research is being done into how best to target this radiotherapy? It seems very powerful, but you’ve got to make this a precision weapon.

Alison. Yeah, absolutely. At the Royal Marsden, we’ve used clinical trials as a way to accelerate progress. Unless you test something you can’t assess the benefit of it, and my colleagues have created some of the trials that have changed the way we treat prostate cancer, for example, over the last ten years. And part of that innovation is in the way we deliver the treatment. We can effectively shape the beams, shape the way the beams deliver their dose around the cancer and spare the normal tissues, which reduces the side effects of treatment.

Kat - One of the problems with cancer is that it’s inside the body, and if you’re directing beams of radiation at a person, surely you have to know where that cancer is inside them. How do you find a cancer inside someone so that you know you’re targeting it?

Alison - Good question. At the moment what we do is we direct our beams based on CT. CT is a fairly standard scan that many people have had. And we have the ability to do CT scans just before the patient has their radiotherapy while they’re on the bed waiting for their treatment. But CT is not really the best way to image cancer. Most cancers are made of soft tissues and bone cancer is very rare.

Soft tissues are better shown by MR scanning - MRI imaging. And that is where the MR Linac, a new machine that we have at the Royal Marsden, will be become very important because we’ll be able to see the cancer much better. Now this is a very technologically difficult thing to do. If you put radiotherapy and a magnet in the same room, they interfere with each other and so it’s taken many years of collaborative developments across the world really to make this a reality.

Kat - One of the other things about human beings is that they move, they breathe, bits of us inside us kind of wriggle around. Does radiotherapy take that into account?

Alison - Yeah. We can do everything we can to set the patient up at the start of their treatment in the right position. But, as we stand here talking, our bladders are filling, our lungs are going up and down. The cancer, if we had any - I hope we don’t - inside them would be moving as well. So, at the moment, the best we can do is put a safety margin around our radiotherapy field to incorporate that movement and make sure we don’t miss the target.

But in the next generation, in the next decade of innovation, we will be able to see the cancer better and track it as it moves during the treatment, and maybe even adapt our radiotherapy beams and our plans during the treatment.

Kat - What are the big questions for the future of research into radiotherapy?

Alison - Our research here, particularly into the MR Linac, which is only one part of our research strategy, we’re working, as well as with collaboration all over the world, with our partners at the Institute of Cancer Research. We’re trying to establish where the MR linac is most able to make things better for patients, where we can change the way we treat cancers, try out new doses of radiation in different way that we hope will be more effective, and cure more cancer with less side effects.

Kat - In terms of reducing the number of hospital visits for radiotherapy, what sort of numbers are we talking about?

Alison - My colleague, David Dearnaley, led a trial called “the trip trial,” which has reduced the standard treatment for prostate cancer down from seven and a half weeks of treatment down to four weeks, and that’s become standard across the NHS already.

We are now conducting the next trial, which is called “the pace trial” led by Nick Vanas, which is comparing the now standard 20 treatment, so four weeks of treatment versus just five daily treatments of radiotherapy for prostate cancer. So a big effect on the patient’s quality of life and their ability to just get on with life and forget they’ve had cancer. But the ultimate goal is to test whether we can got to the ultimate in radiotherapy - can we cure prostate cancer with a single treatment? We don’t know the answer to that yet, but that’s where our research should go over the next decade.    

Kat - Just one dose. That’s almost the “nuke it from orbit” approach. Is that going to work?

Alison - As with every innovation you have to test it robustly. You’ve got to start in a very safe and controlled way and test this kind of treatment on patients that you think will benefit from it. Then, if the initial data is promising, then expand it to a bigger number of patients. But this is very much the future vision, the blue sky vision, and we don’t yet know if this will turn out to be the right thing but there are theoretical reasons why it should. Prostate cancer is very sensitive to bigger amounts of radiation in a single dose and so there’s a theoretical reason why giving just one treatment might work in prostate cancer.

Kat - Alison Tree from the Royal Marsden Hospital. As Alison just explained, of the newest developments in radiotherapy is the ability to combine imaging - being able to look at tumours inside the body - with delivering the radiotherapy.

At the Royal Marsden Hospital, together with The Institute of Cancer Research, they’ve just unveiled something known as an MR Linac - a brand new state-of-the-art device that marries a magnetic resonance imaging, or MRI, scanner with a Linac - the machine that produces the radiotherapy beams.

Funded by the UK Medical Research Council it’s one of only two in the country, with the other still under construction up at the Christie Hospital in Manchester. Professor Uwe Oelfke, leader of the Radiotherapy Physics Modelling group, introduced me to this new piece of kit, which sounds more like a steam train than a medical device...

Uwe - This is the MR Linac facility at the Royal Marsden Hospital in Sutton, and we are standing between the operating room, operating this new machine and the facilities for handling the patients.

Kat - What are the benefits then of being able to see exactly where you’re treating someone, where you’re delivering this cancer killing dose of radiotherapy?

Uwe - The advantages are twofold. First, if you concentrate the radion just within the tumour, this enhances the probability that a tumour is controlled. And secondly, of course, every exposure of healthy tissues induces, to some level, toxicities, and these toxicities are also reduced.

Kat - So you’re going to reduce side effects and then, hopefully, enhance the treatment?

Uwe - Yes. We can use this; it’s called the therapeutic window between tumour control and normal tissue complications. And we can either use the same dose for the tumour and reduce toxicity, or we can use the reduced toxicity to enhance the dose within the tumour to dose escalate the tumour such that the tumour control will go up, while the toxicity still stay in tolerable limits.

Kat - How will this new treatment be used?

Uwe - This new treatment will be first used to really dynamically adapt the radiation fields to the anatomy we are treating. So this is still purely anatomically based but the next step with this kind of machine, you can also take other images. Not just anatomical images but functional images which basically inform you about how much oxygen is available in a tumour. These kinds of functional images then could guide further how we dose a tumour.

For instance, it is well known that tumours are lacking oxygen, that you need more radiation dose and these kinds of effects, at the moment, we cannot really take into account, or it’s very difficult. With this machine, first step is purely anatomical guidance and the next step would be biological guidance.

Kat - We’re currently in the facility and it’s completely quiet - there’s hardly anyone here. So, obviously, it’s not treating any patient’s right now. When will patients start to be treated here?

Uwe - We are hoping that the first treatments will either start this December or at the beginning or next year.


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