IMRT (Intensity Modulated Radiotherapy)

Radiotherapy is the most cost effective treatment for cancer. It is used in all tumour types. It is used to cure cancer, as an additional therapy after successful surgery or chemotherapy and may be used to help with difficult symptoms such as pain and breathlessness.

The Sussex Cancer Centre delivers radiotherapy using 4 Linear accelerators. These machines represent the most modern form of radiation delivery and all of the machines have been purchased and commissioned within the last 5 years.

The beam of radiotherapy may be shaped by the use of small robotic 'leaves' hidden within the head of the machine and driven by a central planning computer. This allows high doses of radiation to be delivered to tumour and a smaller dose to be given to the normal tissues surrounding the tumour. This is called 'conformal' radiotherapy.

Intensity modulated radiation therapy is a specialised form of conformal radiation therapy. This enables the high dosage of radiation to be contoured more closely to the 'target' volume (tumour and adjacent tissue at risk) than was previously possible. The volume of normal tissue receiving a high dose is thereby reduced. There are very few centres that offer this type of radiotherapy at present.

IMRT is achieved by delivering multiple fields of radiotherapy of differing sizes layered on top of each other. A standard radiotherapy treatment for prostate cancer for example may use 4 large fields delivering one portal (beam of radiotherapy) each , IMRT may use up to 6 portals delivered from 9 different positions (a total of 54 small beams!). The Linear accelerators at the Sussex Cancer Centre are capable of delivering IMRT and the Centre has been involved in research work testing these state of the art techniques in a limited way. The calculations required to plan the treatment for each individual patient are enormous and may take even the most powerful computers 8 hours of processing time.

Current planning software available at the Sussex Cancer Centre will not allow the machines to work to their full potential, neither will it allow the Centre to develop its' IMRT program and offer this to future patients. The system that has been purchased for the Centre is 'upgradeable' and these extensions to the system will allow full capability by computing multiple leaf and accelerator positions and their effect in each individual patient.

At present this technology is only available to patients in Sussex by travelling to the Royal Marsden in London. This treatment may often take several weeks and the journey is debilitating. We would dearly love to expand our service so that this therapy could be offered locally and the service expanded to ultimately deliver IMRT for the majority of cases.

Dr. Richard Simcock