Radiotherapy techniques
New radiotherapy techniques and equipment allow clinicians to target tumours with more accurate doses of radiation than ever before. Greater accuracy means that stronger doses can be delivered to tumours while minimising damage to healthy surrounding tissue.
Find out more about modern radiotherapy techniques below.
Intensity modulated radiotherapy (IMRT)
IMRT is a technique which uses linear accelerators to deliver conformal radiation – radiation which is sculpted to the shape of the tumour. It is estimated that one in three patients having radiotherapy could benefit from IMRT, and the national cancer strategy advocates making IMRT more accessible for patients.
IMRT utilises the multi-leaf collimators on a linear accelerator to vary the radiation beam intensity around a target field. The shape of the radiation beams may change hundreds of times during the course of treatment. The intensity of the beams and the direction from which they are delivered also varies. The result is radiation sculpted in three dimensions around the tumour, minimising radiation dose to normal tissue.
Clinical evidence supports that IMRT is effective for certain patients with tumours of the head and neck, breast, prostate, pancreas, lung, central nervous system and where a tumour is close to an organ at risk. Some of these patients may be essentially untreatable without IMRT as an option.
Volumetric modulated arc therapy (VMAT)
VMAT is a new arc therapy technique first implemented in the UK at The Royal Marsden. This kind of radiotherapy is also called RapidArc – both names are specific to the equipment manufacturers, but are the same technique.
Using three-dimensional volumetric imaging, treatment can be designed and delivered to maximise the radiation dose the tumour receives and minimise exposure of the surrounding healthy tissue. The angle of the beam, the dose rate and the linear accelerator's leaf speed are all independently controlled, making this a very accurate form of treatment. Arc therapy treatments also take much less time to deliver than other radiotherapy techniques because beams are delivered in an uninterrupted sweeping arc around the patient.
Stereotactic radiotherapy
Stereotactic radiotherapy is a technique that allows for pin-point, sub-millimetre accuracy when targeting a tumour volume. This precision means that high doses of radiation can be delivered to the tumour, minimising radiation to surrounding organs at risk and decreasing the number of treatments a patient needs.
Stereotactic radiotherapy is most often used on small, well-defined tumours. It is an established treatment for early-stage lung cancer and has also been shown in trials to be effective for patients with inoperable tumours. It is usually delivered using a linear accelerator but there are also machines designed specifically for this purpose, such as CyberKnife.
CyberKnife is a new machine that has just been installed at The Royal Marsden to deliver the latest in stereotactic radiotherapy. It uses a moving couch and a small linear accelerator on a robotic arm to deliver multiple beams of highly concentrated radiation from different angles. It can also adjust for the movement of tumours, for example to match a patient’s breathing motion.
Image-guided radiotherapy (IGRT)
IGRT is the use of a variety of imaging techniques, such as X-rays or CT scans, alongside radiotherapy. Imaging enables the position of the patient and the tumour to be tracked and confirmed so that the radiation beam can be targeted more precisely.
Some of the newest imaging systems include Calypso and ExacTrac, both of which provide precise, real-time tumour tracking for patients undergoing radiotherapy treatment. Both of these are in use at The Royal Marsden.