Radiotherapy is the use of radiation beams to treat and destroy cancer cells and can be used either externally (conformal beam radiotherapy or Intensity Modulated) or internally (brachytherapy) to treat prostate cancer.

External beam radiotherapy focuses radiation using 3D computerised imaging to target the shape and extent of the cancer reducing the damage to healthy surrounding tissue.

Intensity Modulated Radiotherapy (IMRT) is a type of external beam radiotherapy which can adjust the dose of radiotherapy given to a specific part of the cancer depending on its shape thereby increasing the dose of radiotherapy given to the central part of the tumour while treating the surrounding area with a lower dose of radiotherapy. IMRT is also able to “bend” the radiotherapy beam to avoid structures that may be otherwise damaged. It is especially useful for men who have larger volume prostate cancer which has spread to the surface of the prostate or seminal vesicles. A newer type of IMRT can now be delivered using a machine called a rapidarc which rotates around the body. This reduces the treatment time and uses a lower overall dose of radiotherapy.

External beam radiotherapy usually involves from 2-6 weeks of treatment, every day 5-days a week for around 10 minutes a day.

Research has shown that the use of hormonal therapy for a period of 3-months prior to radiotherapy increases the chance of cure.

External beam radiotherapy can be used to treat T1, T2 and T3 prostate cancer, however if T3 (locally advanced) disease is present hormonal therapy will usually be continued for 2-3 years afterwards.Before external beam radiotherapy is started the prostate gland will be visualised in more detail with the use of CT scans and the area to be treated will be marked.

Sometimes movement of the prostate gland can occur within the body for instance due to breathing and this could cause the area which has been marked for radiotherapy to change. If the prostate moves 6mm out of position the radiotherapy treatment may miss the prostate and affect tissue around it such as the bowel. It may be recommended therefore that 3 small gold markers (about 2mm in size) called fiducial markers be inserted into the prostate before radiotherapy in a similar manner to how a prostate biopsy is performed. This allows more accurate targeting of the prostate even if it moves slightly. These markers will remain in the prostate permanently but should not cause any medical problems.


Internal radiotherapy called brachytherapy is the use of minute radioactive seeds that can be implanted into the prostate under a minor operation (permanent brachytherapy). These seeds will decay (die) and give off radiation which can kill cancer cells. This type of treatment will usually only involve 1-2 hospital visits and does not usually require the use of hormonal therapy beforehand.


Brachytherapy is used to treat T1 and T2 prostate cancer. Brachytherapy is ideally suited  to men with a PSA level below 15 and a prostate gland that is less than 50cc in volume. It is not recommended for men who may have had a type of surgery to their prostate called a Trans Urethral Resection of the Prostate gland (TURP).

For more information on brachytherapy (planning) for prostate cancer from the British Association of Urology Surgeons (BAUS) please click here

For treatment please click here

A type of non-permanent brachytherapy can be used to treat prostate cancer either on its own or in conjunction with external beam radiotherapy and is called High Dose Brachytherapy. This involves inserting radioactive rods into the prostate for a day or more in conjunction with external beam radiotherapy. This type of treatment is not standard practice in the UK but may be discussed with men.

There are also a number of newer radiotherapy techniques which use sophisticated imaging techniques to enhance the targeting of prostate cancer. Examples include stereotactic radiotherapy (Cyber knife) and proton beam therapy. These are not widely available everywhere in the UK but may be available within the private sector or under certain circumstances within the NHS if funding is obtained. Their is no current evidence to suggest that they have a significant benefit in reducing side effects which can occur after any radiotherapy treatment.

For general information on radiotherapy from NHS Choices please click here.


I have heard about a new type of radiotherapy called proton beam therapy. Is this an option for me?


External beam radiation releases the maximum dose of radiation soon after penetrating the skin on its way to the tumour and again as it passes through and beyond the tumour. Proton Beam radiotherapy uses a different type of radiation which can be targeted directly at the tumour site and then stop. It can also be used to release much of its energy at precise depths. Specialists who advocate Proton Beam radiotherapy claim it may cause less damage to surrounding healthy tissue.Although proton therapy has been available for some time to treat difficult types of tumour such as brain tumours and children’s cancers it is not standard practice in the UK for prostate cancer. Treatment for prostate cancer with proton beam therapy is currently performed outside of the UK. A more precise type of proton beam therapy using a very thin beam of radiation (pencil beam radiotherapy) to treat prostate cancer is also being evaluated in Europe and America.


Possible side effects of radiotherapy

Erectile Dysfunction

Radiotherapy can affect the nerves surrounding the prostate that control a man’s erections. This may be less than in prostatectomy but maystill occur.There are several treatments for ED and further information can be found here.

Urinary problems

Radiotherapy does not usually cause urinary incontinence but sometimes it may cause a narrowing of the urethra which may then cause difficulties passing urine. This tends to occur  some years following treatment.

Bowel problems

Radiotherapy can cause inflammation to the lining of the rectum in a small percentage of men. This may be temporary or occasionally permanent. It may cause bleeding from the back passage or the need to go to the toilet to pass stool more frequently.

Follow up

After radiotherapy treatment it may take over a year for the PSA level to adjust to an accurate level. It will usually rise gradually and then plateau off. The lowest point at which it reaches is termed the nadir. If the PSA level increases to its nadir value plus 2 then there is more chance that the cancer has returned. If men are receiving hormonal therapy after radiotherapy then the PSA level will be minimal due to the action of the hormone therapy suppressing the PSA value. It will take some time after stopping hormone therapy before the PSA level adjusts in a similar manner.

For older men recurrent prostate cancer may not reduce their life expectancy and it is usual to wait for a rise in PSA level to around 20 before initiating any treatment. At this level a man could commence hormonal therapy which would be likely to control and potentially regress prostate cancer for many years.If cancer returns following radiotherapy then prostatectomy (removal of the prostate gland) is not recommended due to the changes that will have occurred in the prostate from the radiotherapy treatment which may increase the risk of side effects such as urinary incontinence. In this situation newer treatments such as HIFU may offer a good chance of controlling disease progression.


Last reviewed April 2021. Next review 2022.


References available on request.

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