Tuesday 28 March 2000
A new high-tech radiotherapy technique which creates 3D beams to curve around the shape of tumours has been developed by Institute of Cancer Research scientists to halt the spread of prostate cancer.
Prostate cancer is the second most common cancer in men, affecting 20,000 per annum, and mortality rates are high - each year it kills 9,400. In up to 40 per cent of cases, prostate cancer spreads to the pelvis, and the side effects of conventional radiotherapy are severe - diarrhoea, bleeding and bowel incontinence. These side effects have until now prevented doctors from giving effective treatment, so cancer in this region is a major cause of death in prostate cancer patients.
Now for the first time, scientists have developed a treatment - Intensity Modulated Radiotherapy (IMRT) - allowing them to shape radiotherapy precisely to the complex shape of tumours in the pelvic region which are curved and wrapped around healthy tissue.
IMRT will allow doctors to give a dose of radiotherapy high enough to sterilise the cancer (33 per cent higher than conventional treatment). Based on a previous study*, experts predict that side effects will be greatly reduced - by up to 75 per cent - so improving quality of life for all sufferers.
Clinical trials are beginning at The Institute of Cancer Research and Royal Marsden Hospital in the spring, with 90 prostate cancer patients whose disease has spread to the pelvis.
As well as having a major impact on prostate cancer treatment nationally and internationally, experts also predict that IMRT could be used to treat a third of all types of cancers.
This is because the new treatment is the first to be able to target tumours which have spread to the pelvic lymph glands, whilst avoiding giving high doses of radiotherapy to the bowel at the same time. Cancer which has spread to this region is often the cause of death because it is so difficult to treat, and once cancer has spread to the lymph glands the disease spreads more easily to other parts of the body.
So IMRT, by allowing higher doses of radiotherapy, should make treatment more effective in not only prostate cancer, but also cervical, bladder, rectal and endometrial cancers within the next 10 years.
And IMRT could also benefit tumours in other parts of the body which curve around healthy tissue, such as lung, head and neck, thyroid, oesophagus and pancreatic cancers. It will be especially suitable for treating cancer in children because it could minimise damage to growing tissue.
Initial trials at the Institute and Royal Marsden Hospital on patients with breast cancer have indicated that IMRT may improve the cosmetic outcome of conventional radiotherapy, leaving less radiation damage and scarring - another potential benefit of the new treatment.
Dr David Dearnaley, Senior Lecturer at The Institute of Cancer Research and Director of the study said: "This is a very exciting time for us. We finally have the technology to 'tailor' radiotherapy treatment to complex 3D tumour shapes, and we are very grateful to The Cancer Research Campaign for supporting this work."
He continued: "Standard radiotherapy involves geometrical beams forming a 'box' around a tumour, which can damage surrounding tissue and leave permanent side-effects. In conformal radiotherapy, developed at the Institute, the beams are formed around the tumour's irregular shape - and it is very successful in tailoring the treatment of cancer localised to the prostate itself.
However, it is not effective in shaping treatment to the curved tumours which need radiotherapy when prostate cancer spreads to the pelvis. Now we are developing the even more advanced IMRT techniques we will be able to mould radiotherapy to convex shapes, like those of a ring doughnut or cup shape, to precisely target these tumours."
Dr Peter Rigby, Chief Executive of The Institute of Cancer Research said: "With funding from The Cancer Research Campaign we were able to develop conformal radiotherapy which, after the success of clinical trials, was rapidly made available in 15 centres across the country. We hope it will soon be more widely available. We anticipate that IMRT will have the same impressive results, and be fully developed and available over the next 5-10 years."
Intensity-Modulated Radiotherapy (IMRT) is the result of the integration of powerful, high-speed computing technologies with sophisticated radiotherapy equipment - and requires very powerful planning computers in order to 'calculate' how individual treatments will proceed.
Where conventional radiotherapy delivers single beams with a uniform dose, the IMRT technique involves beams made up of hundreds of small components.
In order to vary the intensity of dosage across each component, the beams are delivered through special robotic 'leaves' known as multi-leaf collimators. These move constantly during delivery of the beam in order to tailor the irradiation dosage to different areas of the tumour. A strict quality assurance programme is applied in order to check that the multi-leaf collimator has moved correctly.
Firstly a very accurate image of the patient's body and tumour is taken using a CT (CAT) scan and this information is fed into a high-speed computer. By directing the computer with 'importance factors' about where irradiation is most and least needed the computer calculates a solution about exactly how to deliver treatment.
Notes to editors:
- Side effects in the IMRT trial will be closely monitored but trials of conformal radiotherapy in prostate cancer at The Institute of Cancer Research and Royal Marsden Hospital have shown that side effects can be reduced by up to 75 per cent.
- The trial is funded by The Cancer Research UK, The Institute of Cancer Research, The Royal Marsden NHS Trust and the Bob Champion Cancer Trust.
- The IMRT multi-leaf collimator was purchased in part through a bequest from the Silcock Estate.
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