Radiotherapy for prostate cancer

Radiotherapy is one of the treatments offered to men with early prostate cancer who are otherwise in reasonably good general health. It is generally offered as an alternative to surgery. Sometimes radiotherapy is used after a prostatectomy for locally advanced or more aggressive cancers, or if there are indications that not all of the cancer has been removed by surgery.

Radiotherapy can be delivered externally via external beam radiotherapy or internally via brachytherapy. Most men who receive radiotherapy as their initial treatment will receive Androgen Deprivation Therapy (ADT) before and after.

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External beam radiotherapy (EBRT)

External beam radiotherapy (EBRT) uses high-energy x-rays to kill cancer cells or injure them so they cannot multiply.

Treatment is planned to ensure there is as little damage as possible to the normal tissue and organs surrounding the prostate. Sometimes this planning involves inserting small pieces of gold metal into the prostate to allow more accurate aiming of the radiation treatment. Modern machines limit radiation exposure to surrounding healthy tissue.

Usually, you will have radiotherapy treatment every weekday for up to eight weeks, often in combination with temporary hormone therapy.

During the treatment session, you will lie on an examination table under the machine that is aimed at your prostate. Each session usually takes about 15 minutes.

Side effects of external beam radiotherapy

You may experience some of the following side effects during EBRT:

  • Sexual dysfunction (impotence) – Problems with erections are common after external radiotherapy due to nerve damage, and may be further aggravated by ADT. Problems may not occur immediately, but may develop over time and be ongoing. Some men notice pain on ejaculation or find that they ejaculate less after, and while, undergoing radiotherapy. This discomfort can ease over time; however, dry orgasms are common after radiotherapy. See our tips for improving quality of erections.
  • Infertility – Radiotherapy to the prostate usually results in infertility. If you wish to have children, speak to your doctor before treatment about sperm banking or other options.
  • Skin irritation – Skin in the treatment area may become red and sore during or immediately after treatment. These reactions fade with time. Ask your treatment team for advice about dealing with this.
  • Tiredness – When your body has to cope with the effects of radiation on normal cells, it becomes fatigued. Fatigue may build up slowly during treatment and should go away when treatment is over, but can last up to six months.
  • Urinary problems – You may experience a burning sensation when urinating, or an increased urgency to urinate. These side effects usually go away after treatment, but your doctor can prescribe medication to reduce any discomfort you may experience. Injury to the lining of the bladder can sometimes cause bleeding. This is called radiation cystitis. Radiation is unlikely to cause incontinence, but it can cause ongoing bleeding that can be difficult to control. It is important to report any problems to your doctor.
  • Bowel problems – Some men may bleed when passing a bowel motion. This is caused by damage to the fine blood vessels in the lower bowel. Let your doctor know if you experience rectal bleeding. Some men may also have diarrhoea or difficulty holding onto their bowel motions. These problems are usually temporary and your treatment team will let you know how to manage these side effects.


Brachytherapy is a type of targeted internal radiotherapy where the radiation source is placed directly within the prostate gland. This allows higher doses of radiation to be given, while the effects on nearby tissues such as the rectum and bladder are minimised. Brachytherapy can be given at either a low-dose rate by inserting permanent seeds that are radioactive for three months, or at a high-dose rate through temporary needle implants. Brachytherapy is not suitable for men who already have significant urinary symptoms.

Low-dose rate brachytherapy

This treatment is most suitable for men with a small to moderate-sized prostate gland, few urinary symptoms, and small tumours with a low PSA level (less than 10) and a low/intermediate Gleason or ISUP score.

Low-dose rate brachytherapy involves implanting radioactive seeds, about the size of a grain of rice, into the prostate. The seeds release radiation to kill cancer cells and lose their radiation effect over a period of three months. The seeds are inserted under a general anaesthetic through the skin between the scrotum and anus using needles and are guided into place by ultrasound.

Implantation takes 1–2 hours and is done under general anaesthetic. There is no incision, only some small puncture holes that heal very quickly, allowing for a faster recovery than external beam radiotherapy or surgery. This is usually a day surgery procedure.

The seeds remain radioactive for three months. Although very uncommon, it is possible that a seed may dislodge during sexual activity. For this reason, you will be advised to use a condom or avoid sexual activity for three months. This way if a seed comes out, the condom will catch it.

High-dose rate brachytherapy

This treatment is usually given to men with higher PSA levels and Gleason scores who are at risk of locally advanced cancer. It is generally combined with a short course of external beam radiotherapy.

High-dose rate brachytherapy is given through temporary needle implants. Hollow needles are placed in the prostate under general anaesthetic and high-dose radioactive wires are passed down the needles. You will usually stay in hospital overnight.

Side effects of brachytherapy

Inserting the radioactive seeds causes minimal discomfort, but side effects may include pain when urinating, poor urine flow and bladder irritation. These are generally temporary and can be managed. These effects usually start 1–2 weeks after treatment and start to resolve within a couple of months.

Impotence and changes in ejaculation may occur after temporary needle implants. Permanent radioactive seeds have the lowest chance of causing erection problems compared with other treatments. Pain on ejaculation and dry orgasms may also occur. Talk to your doctor and/or treatment team about the best ways to manage these side effects. 

Video: What is radiotherapy?

Watch this short video to learn more about radiotherapy.

This information was last reviewed in April 2016
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