A trial comparing the outcomes of different treatments for prostate cancer (CHRONOS A)

Please note - this trial is no longer recruiting patients. We hope to add results when they are available.

Cancer type:

Prostate cancer




Phase 2/3

This trial is comparing treatment to the whole prostate with treatment to only the areas of cancer in the prostate. 

There are 2 parts to the CHRONOS trial. This is the summary of CHRONOS A. You can read about the 2nd part CHRONOS B

More about this trial

When there is a lot of cancer in the prostate doctors treat the whole prostate. This can be either by:

This called radical therapy. This controls the cancer but there are side effects. 

There are treatments that target only the areas of cancer in the prostate. These are:

This is called focal therapy. Some research shows that focal therapies might control the cancer as well as radical therapies. And that the side effects aren’t as bad. 

But there hasn’t been any research that compares how well radical therapies and focal therapies control prostate cancer. And the differences in the quality of life of the men having these treatments. This is what the researchers want to do in this trial. 

The aims of CHRONOS A are to find out:

  • if people are willing to agree to take part in a randomised clinical trial Open a glossary item comparing focal therapy with radical therapy
  • if focal therapy is as good as radical therapy for controlling prostate cancer   
  • what people think about the treatments
  • more about the side effects of each type of therapy
  • how each therapy affects quality of life Open a glossary item 

Who can enter

The following bullet points list the entry conditions for this trial. Talk to your doctor or the trial team if you are unsure about any of these. They will be able to advise you. 

Who can take part

You may be able to join this trial if all of the following apply. You:

  • have adenocarcinoma prostate cancer 
  • have a prostate specific antigen (PSA) Open a glossary item of 20ng/ml or less 
  • have a Gleason score Open a glossary item of 7 or 6 
  • have had an MRI scan Open a glossary item before having tissue samples (biopsies Open a glossary item) taken to diagnose your prostate cancer. If you couldn’t have an MRI scan you must have a transperineal mapping biopsy 
  • are at least 18 years old

Who can’t take part

You cannot join this trial if you have already had treatment for prostate cancer. 

Trial design

This is a phase 2/3 trial. In total the researchers need 1,190 men to join. 

There are 2 stages to CHRONOS A. 

In the 1st stage the team need 60 people to join. This is a pilot study to find out whether people are willing to join the trial and be put into the different treatment groups. 

In this part when you see your doctor to talk about the trial a member of the research team will ask to record the appointment on audio tape.  

The research team member might also ask to interview you. The team will arrange this at a time and place convenient for you. 

You don’t have to agree to your appointment being taped or to the interview if you don’t want to. You can still take part in the trial. 

You can agree to have your appointment being taped or to the interview but not take part in the study if you don’t want to. 

The 2nd stage of CHRONOS A will open if stage 1 is successful. 

Those who do join part 1 continue into part 2. 

In the 2nd stage of CHRONOS A the team need a further 1,130 men to join. 

This is a randomised trial. You are put into a treatment group. Neither you nor your doctor can choose which group you go into. There are 2 groups:

  • radical therapy 
  • focal therapy

There are different radical treatments and focal treatments available in both groups. Your doctor will talk to you about which might be the best treatment for you. 

Radical therapy
You have 1 of the following treatments:

External beam radiotherapy (EBRT) uses high energy beams similar to x-rays to destroy cancer cells. A machine directs these beams at the cancer. Before your treatment the team plan very carefully where to direct the beams and how much radiotherapy you need. You have treatment Monday to Friday. 

Brachytherapy is a type of internal radiation therapy. It is when a radioactive source is put inside the prostate. It then releases radiation to destroy the prostate cancer cells. The source is also known as seeds or pellets. These might stay inside your prostate permanently. Or your radiographer or doctor will remove them after treatment. 

You have brachytherapy as a day case and it takes 1 to 3 hours. You might have a local anaesthetic Open a glossary item or a general anaesthetic Open a glossary item

Prostatectomy is surgery to remove all your prostate gland. This might include removing the surrounding lymph glands Open a glossary item. You have a general anaesthetic. You stay in hospital for 1 or 2 nights after surgery. 

Focal therapy
You have 1 of the following treatments:

HIFU is high intensity focussed ultrasound. HIFU uses high frequency sound waves targeted at the cancer cells. The waves create heat that destroys the cancer cells. 

To have the treatment you have an ultrasound probe put into your back passage (rectum). This probe gives out high intensity ultrasound energy that can destroy the cancer cells in your prostate. The high intensity ultrasound energy travels through the back passage to the prostate. 

You have HIFU as a day case. It takes about 1 to 3 hours. You have a general anaesthetic so you're asleep. At the start of treatment you have a tube (urinary catheter) put into your bladder through the hole in your penis. This might stay in for up to a week to drain urine from your bladder. A nurse will show you how to care for the catheter if you do go home with it.  

Cryotherapy uses extreme cold to destroy cancer cells. The doctor puts thin needles into your prostate. The needles go in through the area between your anus and testicles (perineum). They then pass a special gas down the needles into your prostate. 

You have cryotherapy as a day case. It takes 1 to 3 hours. You have either anaesthetic put into the fluid around your spinal cord Open a glossary item (spinal anaesthetic) or a general anaesthetic.

Before they start the cryotherapy treatment your doctor puts a tube (warming catheter) in through the hole in your penis into your bladder. This helps protect the tube where urine passes (urethra) from the bladder out of the body from possible damage.

You might need to have another treatment of HIFU or cryotherapy if a scan or tissue samples shows there still might be cancer in your prostate. Your doctor will talk to you about this. 

Quality of life questionnaire
You fill in a questionnaire:

  • before starting treatment
  • during treatment 
  • for up to 5 years after treatment

The questions ask about:

  • any side effects 
  • your daily activities
  • general heath

You can choose to fill the questionnaire in:

  • when you see your doctor 
  • by telephone – a member of the research team will call you
  • by email – to a secure NHS account

Extra samples for research
You give extra blood and urine samples before and during treatment. 

You have prostate tissue samples (biopsies) taken as a part of your routine care. Your doctor takes these when you are diagnosed and at times during your treatment. The research team want a small piece of these biopsies. 

Researchers want to use these samples to help improve the diagnosis and the treatment of prostate cancer. 

Imaging scan information
As a part of the trial you have scans of your prostate to see how treatment is working. The research team want to store these scans and use them to see if there is a better way to identify prostate cancer. 

You don’t have to agree to this. You can still take part in the trial. 

Health information
The team want to know what happens to your health after the trial has finished. They do this by looking at your health records held by the NHS. 

You don’t have to agree to this. You can still take part in the trial. 

Hospital visits

You see the doctor for some tests before taking part. These tests include:

  • physical examination
  • blood test
  • urine test
  • PSA blood test
  • MRI scan if you are in the focal therapy group and haven’t already had an MRI scan using a contrast dye Open a glossary item

You see the doctor after treatment at:

  • 3 months
  • 1 year and then
  • every 6 months for 5 years

You have the same tests as before. 

People in the focal therapy group have an MRI scan at 1 year.  

Please note
If the pilot study (stage 1) is not successful then the larger trial won’t go ahead. In this case people in the pilot study are followed up by the team for at least 3 months. After this you have routine follow up which your doctor will tell you how often that is. 

Side effects

The trial team monitor you during treatment and afterwards. Contact your advice line or tell your doctor or nurse if any side effects are bad or not getting better. 
Side effects from external radiotherapy, prostatectomy and brachytherapy can include:

  • leaking of urine
  • problems getting an erection
  • changes to your bowels including diarrhoea and inflammation

We have information about the side effects of:

We have information about:

Recruitment start:

Recruitment end:

How to join a clinical trial

Please note: In order to join a trial you will need to discuss it with your doctor, unless otherwise specified.

Please note - unless we state otherwise in the summary, you need to talk to your doctor about joining a trial.

Chief Investigator

Hashim Ahmed

Supported by

Imperial College London
Prostate Cancer UK
Imperial Clinical Trials Unit (ICTU) 

If you have questions about the trial please contact our cancer information nurses

Freephone 0808 800 4040

Last review date

CRUK internal database number:


Please note - unless we state otherwise in the summary, you need to talk to your doctor about joining a trial.

Keith took part in a trial looking into hormone therapy

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"Health wise I am feeling great. I am a big supporter of trials - it allows new treatments and drugs to be brought in.”

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