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What are clinical trials?

An overview of clinical trials and how they may relate to you

What are clinical trials?

As a new medicine or procedure moves from the lab to the clinic, it goes through several stages of research.  

A clinical trial is usually the last stage of this process, and involves people with, or at risk of, prostate cancer.  Clinical trials help researchers work out if the new medicine or procedure they’re developing can prevent, diagnose, treat, or manage prostate cancer in real life situations – and, most importantly, if it’s safe. 

That’s why clinical trials make up a vital part of our research funding at Prostate Cancer UK. 

Some of the questions a clinical trial could help answer include: 

  • Is the new treatment or procedure safe? 
  • Is it effective, and is it better than the current approach? 
  • Does it cause side effects, and how serious are these? 
  • For a treatment, what dose makes it most effective while keeping side effects to a minimum? 

Often when clinical trials are high quality they may be randomised, blinded and tested against a placebo or the current best treatment. Below is a brief overview of what these terms mean. For a more comprehensive, in-depth breakdown of clinical trials please see our health information pages.


Randomisation is the process where all the men taking part in a trial are randomly assigned to different groups, often by a computer. Neither you nor your medical team can choose a group. Randomisation is one method researchers use to make sure trials are less at risk of bias.

In practise, randomisation is used to split men across the many different groups researchers have created in a clinical trial. One group of men will get the new treatment. The others, have the current standard treatments or a placebo. The researchers can then compare results from the different randomised groups.


Blinded refers to the process which ensures both men and often healthcare teams do not know which treatment you are receiving after being randomised. Trials are blinded as knowing what treatment you are getting can influence how you respond to it. It also aims to prevent bias from your healthcare team, as they cannot make choices on your treatment using their existing knowledge.


Placebo refers to a dummy treatment. Often these look and feel the same as the treatment or procedure that is being tested. It might be a tablet containing an inactive ingredient that won’t have a biochemical effect. People often feel better when they have a placebo because they think they are having a real treatment. This can cause real changes in your sense of wellbeing and is known as the ‘placebo effect’.

Why are clinical trials important?

Without clinical trials it would be almost impossible to get better and more accurate diagnostics, more effective treatments with fewer side effects, and ultimately better care for men. 

We fund and support researchers to bring their ideas and innovations to life. We understand the journey of taking an idea from the lab to the clinic is a long but absolutely vital journey. All clinical trials look to ensure men get real life benefits, with the least harm. It's this data that lets us know whether something is better than the current gold standard. 

Our funded research has helped bring real life tangible change to clinical practice and therefore the treatments available to men.

While research does take time, it can extend lives. 

When I was referred, I was given the option to have the biopsy there and then or to go on a trial – PROMIS. I chose the trial and I honestly think that decision saved my life. Not only did this research help me, it’s changed how people are diagnosed, so men in future – like my son Adrian – will get better tests too."
Allan Roper, Based in Hampshire

What are clinical trial phases?

Clinical trials testing new treatments and medical procedures are split across different phases. The different phases aim to establish new information about the new treatment. This information is vital for researchers to work out all the details of how and why a treatment or procedure works, and can ultimately, go on to benefit men.

Early phase trials look at whether the drug is safe in humans and the side effects it may cause. Later stage trials look to compare the new treatment with currently approved treatments – this tells researchers whether a drug is better than alternatives or not. Click the drop down options below for a brief overview of what is studied in each phase. 

A phase 0 trial uses a very small number of participants and generally the researchers look to test whether the treatment is safe at very low doses. This is usually not randomised. 

A phase I trial generally has a small number of men (20-80). The primary focus of Phase I trials are to find safe doses,  check for side effects and to study what the treatment does to the body. This is vital information for the researchers to take their treatment/procedure further.  

A phase II trial usually involves men in slightly larger numbers (100-300). Here, dose of drug is further tested and for the first time researchers will look at how effective the new treatment is.

A phase III trial involves men in larger numbers (1000-3000).  Here, the research team compares the current gold standard treatment, or placebo, with the new treatment/procedure. Often these phases are randomised and blinded to prevent bias. 

A phase IV trial looks at large numbers of men in follow up after the drug has been approved and is being used. This aims to study side effects and best uses of the drug. The research team looks at this data over periods of time up to 10 years after receiving the treatment. This really ensures treatments are being used in the best way possible for men.

Where can I find out more about clinical trials and what they mean for men?

This page has hopefully given you a brief overview of the processes involved and some of the technical terms to help understand what the researchers are doing. There is plenty more information to be found across our website. If you are interested in seeing what trials we fund and where they take place, you can find these on our interactive map. 

For a deeper dive into how trials work and whether they may be right for you we have more detailed information on our clinical trials pages. 


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