How clinical trials are planned and organised

This diagram shows the process that reseachers follow to set up and run a clinical trial. There is more information about each of the stages below.

How trials work

Having an idea

Researchers or doctors have an idea of something they would like to test. This could come from laboratory work, other trial results or experience with patients. The idea could involve:
  • a new treatment 
  • a different combination of treatments
  • using an existing treatment for a different condition
  • testing a new way of giving an existing treatment

Writing the plan

The team interested in doing the trial write a detailed plan (protocol) that everyone involved in the trial will use. It contains lots of information, including:
  • why they want to do the trial
  • who will be able to take part (the eligibility criteria)
  • how many people they need to take part
  • what the treatments will be
  • what tests and appointments people will have before, during and after treatment
  • how and when they plan to analyse the results

Peer review

Doctors, researchers and statistics experts who are not involved with the trial then check the protocol to make sure it is ok. They look at all aspects of the trial including:
  • how important the research question is
  • how easy it is likely to be to recruit patients
  • whether they plan to analyse the results in the right way
  • if there are any possible difficulties the research team have not though of


The research team will need money to run the trial. This may come from a charity, the government or a pharmaceutical company. Read more about how trials are funded

Ethical approval

The protocol must be approved by an ethics committee. They must make sure it is in the best interest of the patients, and will be possible to run. Read more about how trials are approved.

Hospitals take part

Once the trial has been given the go ahead, hospitals with the right expertise and equipment can sign up so they can recruit patients to the trial. The staff involved will usually have some training from the research team.

Patients join the trial

All trials have entry conditions called eligibility criteria. Once the trial is up and running, patients who fit the criteria can take part. 
The research team must give everyone who wants to take part all the infrormation they need. This includes what is involved and all the possible advantages and disadvantages
Once they have read the information and asked any questions they have, they sign a consent form to say they are happy to join the trial. Find out more about what you should be told.


The people taking part can start treatment once they have been given all the information they need and signed a consent form. 
Depending on the design of the trial, they may be put into one of the treatment groups at random. This makes sure the different trial groups are even and means the results are more reliable. Learn more about randomised trials.

Analysis of the results

Once everyone taking part has had treatment, the research team will look at and analyse the results. They will then draw some conclusions about the treatments in the trial. And they may make recommendations for future research.
Many research teams publish the results in a medical journal or present them at a conference, to share what they have learnt.
Sometimes the results show that the new treatment is not better than the existing treatment. But even when a trial shows a treatment isn’t useful for a particular cancer, it adds to our knowledge and understanding of cancer and how to treat it.

Licensing new treatments

If the results of the trial show a new treatment is better than the existing treatment, it may be licensed so that doctors can prescribe it. This is quite a long and complicated process, and often depends on the results of more than trial. 
Find out more about how drugs are licensed.

Data monitoring committee

The data monitoring committee (DMC) is group of people who are not directly involved with the trial. They keep an eye on how things are going all the way through, and make sure everything is running safely. They change parts of the trial, or even stop the trial, if they feel they need to.  
Learn more about how trials are monitored.

Related information


Last reviewed

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

Find a trial

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