External beam radiation therapy (EBRT) uses one or more beams to deliver high energy x-rays from outside the body to the cancerous area. Treatment is usually given over 4–8 weeks; each treatment is about 15 minutes.
Types of EBRT which can be used for the treatment of prostate cancer include:
- Intensity modulated radiation therapy (IMRT) – a high precision type of radiation therapy that uses computer controlled linear accelerators to deliver high dose radiation to cancerous tumours in the prostate
- Volumetric modulated arc therapy (VMAT) – a novel radiation therapy technique that delivers the radiation dose continuously as the treatment machine rotates. This technique accurately shapes the radiation dose to the tumour while minimising the dose to surrounding organs. VMAT can be used to treat large areas of the body with uneven boundaries and tumours located close to vital organs, such as prostate cancers, without fear of damage to these organs by high doses of radiation
Image guided radiation therapy (IGRT) is used to ensure EBRT is delivered as accurately as possible. This involves advanced imaging equipment and computer software such as MRI, CT and x-ray to increase the radiation therapists ability to precisely target a tumour with radiation beams.
Ensuring your radiation therapy treatment is highly-accurate
As part of your external beam radiation therapy treatment, you may have Calypso® radiofrequency transponders surgically placed in your prostate tumours to track and adjust radiation treatment beams due to natural movements of the body, such as breathing. The transponders are small, approximately 8mm long – about the size of a grain of rice. This helps ensure that radiation therapy is delivered accurately to a smaller treatment area and less radiation is delivered to surrounding healthy tissue, reducing side effects.
Fiducial markers (gold seeds) are also sometimes used at the discretion of your radiation oncologist, which help to more accurately locate the prostate gland during radiation therapy treatment.
If your treatment is being delivered using the Varian TrueBeam linear accelerator (radiation therapy machine), triggered imaging technology may be used. This enables visual verification that a tumour is being accurately and precisely targeted and is specifically used for prostate cancers. Using markers implanted in the prostate, radiation therapists can visualise your tumour throughout treatment using low dose x-ray images which allow the machine to automatically detect the position of the markers.
Reducing your risk of side effects
Your doctor may talk to you about having SpaceOAR Hydrogel implanted by a urologist ahead of your treatment. SpaceOAR Hydrogel is a gel-like substance that is implanted between the prostate and rectum to reduce side effects during radiation therapy treatment. As the rectum and prostate are very close and separated by only a small space, the rectum can be affected by radiation to the prostate. SpaceOAR Hydrogel moves the rectal wall away from the prostate, protecting the rectum from being damaged during radiation therapy.