UPDATE - Issue 14 - April 2003
A new treatment technique in Radiotherapy
Radiotherapy is frequently prescribed as a means of curing or, at least, reducing the size of cancers of the prostate. The intensity of the radiation is what kills the cancer cells. Unfortunately the same level of radiation will also kill normal cells. Standard radiotherapy involves two or more beams of radiation striking the body from different angles. Only where these beams meet is the radiation of sufficient strength to destroy cancerous and, regrettably, normal cells.
Conformal radiotherapy uses the same radiotherapy machine (called a Linear Accelerator) as the normal treatment but uses metal blocks placed in the path of the x-ray beam to alter the shape of the beam. This means that the metal blocks can be carefully planned for each patient to shape the treated area more precisely and so reduce the amount of bowel and bladder tissue that is irradiated. A number of centres in the UK now offer conformal radiotherapy. In theory, it is more effective in providing a high dosage of radiation to the tumour while keeping radiation to normal tissue to a minimum.
More recently a device called a multileaf collimator has been produced as an alternative to the metal blocks. This consists of a number of layers of metal sheets which are fixed to the Linear Accelerator. Each layer can be adjusted to a different position and so alters the shape and intensity of the beam of x-rays reaching the patient. This means the settings of the multi-leaf collimator can simply be changed for each patient's treatment and there is no need to make special metal blocks.
A further development to move the collimator during the radiotherapy treatment gives even more precise shaping of the treatment areas. This is called intensity modulated therapy.
As far as we know there are no centres in the UK that yet offer intensity modulated radiotherapy. Dr Roger Macklis at the Cleveland Clinic Foundation in Ohio is one of a number of physicians in the US who are now treating prostate cancer patients with this technique.
At the moment although conformal therapy has theoretical advantages over standard treatment the case for its routine use remains to be proven. The Medical Research Council has a trial under way to clarify this issue but it will be some years before the results are available. Recently issued national guidelines for the use of radiotherapy in the management of prostate cancer make no specific recommendations for the use of conformal or, indeed, intensity modulated therapy.
We are grateful to CancerBacup for some of the information in this article.