The first step in external beam radiotherapy is to have a special planning scan (CT scan) of your pelvis. This is done to see exactly where in the prostate the cancer is and whether it has spread to areas around the prostate gland or other parts of your body. The information on this scan will allow your doctor (oncologist) to see exactly where your prostate is and map the areas that need treatment.
During the scan the doctor will place small, permanent marks (dots the size of a freckle) of ink onto your skin. These permanent ‘dots’ will be used to ensure that the exact same area is treated for each of your treatment sessions.
The doctor may ask a radiotherapy physicist to make an individual plan for your treatment. They will use a computer program to decide exactly where the X-rays need to be aimed to treat your prostate gland while trying to avoid as much of the normal tissue in the surrounding areas (bowel, bladder) as possible. This process is very complicated and can take up to a few weeks to be completed.
When the doctor is satisfied with your plan, you may need to go back to the radiotherapy department for one further visit for a final check to position the X-ray beams before the actual treatment starts. (This is known as a verification visit.)
The X-rays are made in a special machine called a ‘linear accelerator’. When you go for treatment, the radiographer will ask you to lie on your back on a firm bed attached to the machine. Part of the machine will move around you and direct X-rays at your prostate from different directions.
The treatment will only take a few minutes and is completely painless. It is important that you lie very still while the treatment is being given. You may be asked to drink some water before each therapy as this will fill your bladder and reduce the amount of bladder tissue in the radiotherapy beam.
You can expect to have between 20 and 40 treatment sessions over four to eight weeks as an outpatient from Monday to Friday (not weekends).
There are two main types of external beam radiotherapy that are available and these use different methods to reduce the amount of radiation given to the normal tissues surrounding the prostate gland. This can reduce side effects and also allow higher doses of radiation to be concentrated on the prostate gland itself.