Externa beam radiotherapy for prostate cancer
Radiotherapy uses high energy x-rays to treat cancer cells. It is a common treatment for prostate cancer. External radiotherapy uses a machine outside the body to direct radiation beams at the cancer.
You have external radiotherapy in a hospital radiotherapy department. You usually have it as an outpatient each weekday over 2 to 8 weeks. Some hospitals have rooms near the hospital you can stay in if you have a long way to travel.
This page is about radiotherapy for prostate cancer that hasn't spread.
Read about radiotherapy for prostate cancer that has spread to another part of your body
There are different types of external radiotherapy. For prostate cancer, these include:
intensity modulated radiotherapy (IMRT)
stereotactic body radiotherapy (SBRT)
Intensity modulated radiotherapy (IMRT)
IMRT is the most common type of radiotherapy for prostate cancer. IMRT shapes the radiation beams to closely fit the cancer. This means that the cancer receives a high dose of radiation and healthy tissues around receive a lower dose.
VMAT is a newer type of IMRT. VMAT stands for Volumetric Arc Therapy and is also called Rapid Arc. During VMAT, the radiotherapy machine moves around you in an arc shape. The machine continuously reshapes and changes the intensity of the radiation beam as it moves around.
Your specialist can tell you what type of radiotherapy is available at your radiotherapy centre.
Find out more about IMRT and VMAT
Stereotactic radiotherapy
Stereotactic radiotherapy is also called stereotactic ablative radiotherapy (SABR) or stereotactic body radiotherapy (SBRT). It gives high doses of radiation from different angles around the body. This means that your treatment team can direct a very high dose of radiation to the cancer. And a much lower dose to the tissues around it.
You have a much higher dose of radiation at each treatment session compared to IMRT. But you have fewer treatment sessions with this type of radiotherapy so the course is shorter.
Stereotactic radiotherapy isn’t suitable for everyone. And it isn't available at all treatment centres.
If your prostate cancer hasn't spread
Cancer that hasn't spread to another part of your body is called non metastatic cancer. You might have external radiotherapy that aims to cure non metastatic prostate cancer. This is called radical radiotherapy. You might have radical radiotherapy for prostate cancer that:
hasn’t spread outside the prostate gland
has spread into the tissues around the prostate gland
Doctors in the UK recommend the best treatment for you depending on your risk group. They use a system called the Cambridge Prognostic Group (CPG).
Read about the Cambridge Prognostic Groups
You may have radical radiotherapy with hormone therapy. Your doctor might recommend this for CPG 2, 3, 4 or 5 prostate cancer.
Find out more about hormone therapy for prostate cancer
Your doctor may also recommend you have external radiotherapy with brachytherapy. This is to try to stop prostate cancer from spreading beyond the prostate.
Brachytherapy is a type of internal radiotherapy. This means that a radioactive source is put inside the prostate. The radioactive source releases radiation to destroy the prostate cancer cells.
Find out more about brachytherapy for prostate cancer
If your prostate cancer has come back
Your prostate cancer might come back after having treatment to try to cure it. This is called recurrent or relapsed prostate cancer. Your treatment options depend on several factors. These include what type of treatment you have already had.
Your doctor might recommend external radiotherapy if your cancer comes back after surgery.
Read more about treatment for prostate cancer that comes back
If your prostate cancer has spread
Cancer that has spread to another part of your body is called metastatic cancer.
For metastatic prostate cancer, you may have radiotherapy to the prostate. Or to other parts of the body where the cancer has spread. This can help to reduce symptoms and help you feel better.
Radiotherapy machines are very big and could make you feel nervous when you see them for the first time. The machine might be fixed in one position. Or it might rotate around your body to give treatment from different directions. The machine doesn't touch you at any point.
Before your first treatment, your will explain what you will see and hear. In some departments, the treatment rooms have docks for you to plug in music players. So you can listen to your own music while you have treatment.
You might need to drink a certain amount of water before each treatment. This is to make your bladder comfortably full. This can help to reduce the movement of the prostate between treatments. It can also reduce the radiation dose to the bladder and keep your bowel out of the way. You have to drink the same amount of water each time so that your bladder is the same size.
The radiographers help you to get into position on the treatment couch. They line up the radiotherapy machine using the marks on your skin.
Then the radiographers leave you alone in the room for up to 25 minutes. They will tell you what to do if you need help during this time.
You need to lie very still. Your radiographers might take images (x-rays or scans) before your treatment. This is to make sure that you're in the right position. The machine makes whirring and beeping sounds. You won’t feel anything when you have the treatment.
Your radiographers can see and hear you on a CCTV screen in the next room. They can talk to you over an intercom and might ask you to hold your breath or take shallow breaths at times. You can also talk to them through the intercom or raise your hand if you need to stop or if you're uncomfortable.
The short video below shows how you have radiotherapy:
This type of radiotherapy won't make you radioactive. It's safe to be around other people, including pregnant women and children.
You might have to travel a long way each day for your radiotherapy. This depends on where your nearest cancer centre is. This can make you very tired, especially if you have side effects from the treatment.
You can ask your radiographers for an appointment time to suit you. They will do their best, but some departments might be very busy. Some radiotherapy departments are open from 7 am till 9 pm.
Car parking can be difficult at hospitals. Ask the radiotherapy staff if you are able to get free parking or discounted parking. They may be able to give you tips on free places to park nearby.
Hospital transport may be available if you have no other way to get to the hospital. But it might not always be at convenient times. It is usually for people who struggle to use public transport. Or who have any other illnesses or disabilities. You might need to arrange hospital transport yourself.
Some people are able to claim back a refund for healthcare travel costs. This is based on the type of appointment and whether you claim certain benefits. Ask the radiotherapy staff for more information about this and hospital transport.
Some hospitals have their own drivers and local charities might offer hospital transport. So do ask if any help is available in your area.
Radiotherapy to the prostate can affect your bladder and bowels. This can mean you might have to pass urine and empty your bowel more often than normal.
Your doctor might offer you a choice of treatments. For example, monitoring the cancer or having surgery or radiotherapy. These treatment choices have different benefits and side effects.
Last reviewed: 25 Jun 2025
Next review due: 25 Jun 2028
Your radiotherapy team needs to plan your external radiotherapy before you start treatment. This means working out the dose of radiotherapy you need and exactly where you need it.
Radiotherapy to the prostate can cause some side effects. These include loose or watery poo (diarrhoea) and problems passing urine.
You might have long term side effects after having external radiotherapy for prostate cancer. These include problems getting an erection and bowel and bladder problems.
Prostate cancer usually depends on testosterone to grow. Hormone therapy blocks or lowers the amount of testosterone in the body.
Get practical and emotional support to help you cope with a diagnosis of prostate cancer, and life during and after treatment.
Prostate cancer is cancer that starts in the prostate gland. The prostate gland is found at the base of the bladder and is about the size of a walnut.
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