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What is a clinical trial? open accordion arrow

A medical research study that involves people, whether healthy or not, is called a clinical trial.  Each stage of the trial is known as a "phase". There are four phases of clinical trial that take place one after the other, but only if the previous phase is successful. 

Clinical trials are used to:

  • understand the risks and causes of disease
  • screen people known to be at risk of developing diseases like cancer
  • test new treatments or combinations of existing treatments
  • investigate options to minimise or control the symptoms of disease and/or the side effects of treatments
Not all treatments will pass all the phases required to become a standard option and not all trials will prove beneficial for the patient involved.
Phase I open accordion arrow

Phase I trials check the safety of a new therapy and take place after laboratory testing has shown that a new treatment, or changing the way existing treatments are given, may be more effective when treating cancer.

People in these trials are normally healthy but will often include patients that have advanced cancer and have exhausted all conventional treatment options available to them. Participants in these trials may or may not benefit from the trial. Phase I trials:

  • include a small number of people (usually between 20-100)
  • are usually the first time a treatment has been tested on humans
  • by starting the trial using small doses, it aims to find out more about the most effective dose to use
  • identify any side effects of treatments
  • may last for a significant length of time
Phase II open accordion arrow

Phase II trials take place after a successful Phase I trial and are carried out in order to understand how well the treatment works.

Sometimes Phase II trials are split into two trials known as Phase IIA and Phase IIB.

  • Phase IIA is designed to work out how much medicine should be given
  • Phase IIB is designed to understand how well the drug works at the prescribed dose(s)

In general all Phase II trials are very similar to Phase I but are:

  • carried out on a larger number of people (typically between 100 and 300 people) who may, or may not, have the same type of cancer
  • aim to understand if a treatment works as well as (or better than) standard treatments
  • aim to understand if a treatment works better in specific cancer types
  • investigate the side effects and dosage to use
Phase III and IV open accordion arrow

Phase III trials are carried out in order to confirm that the findings of the previous phases are still true in an even larger patient population.

Generally they:

  • Include much larger numbers of patients (usually >1000)
  • Compare treatments to existing treatments or a placebo to test whether the new treatment works better
  • Continue to check for side effects
Phase IV trials test long-term safety in a diverse patient population. These trials take place once a treatment has passed all the previous phases and the treatment is available on prescription. Some people that have not been tested in Phases 1- 3 may show adverse reactions during a phase IV trial. Not all treatments will go into a Phase IV trial.
Benefits of clinical trials open accordion arrow

Clinical trials are used to understand if a particular treatment is better than another but may not benefit the participant personally.

This means that your treatment and progress could be monitored more closely than when you undertake standard therapies. Once the trial has finished, it might be possible for your doctor to offer you more appropriate and effective treatment to you.

Clinical trials are essential for the development of new and better treatments. They may help you get more information for your future treatments. You will be helping the NHS learn what the best possible standard of care is and how that care should be given in future.

Disadvantages of clinical trials open accordion arrow

There can be some disadvantages to taking part in a clinical trial. This is because no one can be 100% sure what the outcome will be for you.

This could be because the treatment is not as effective as hoped when compared to standard treatment. You may develop unexpected side effects. You may have to have more tests or visits to the clinic than you would if you were receiving the standard treatment for your disease.

Questions to ask your doctor about clinical trials open accordion arrow

When deciding whether to participate in a clinical trial or not, there are a number of questions you may wish to ask so that you understand what impact the trial may or may not have on you. 

Some questions that you may wish to ask your doctor include:
  • What is the purpose of the trial and how will it help people like me?
  • Who is paying for the trial?
  • How long will the trial last and how long will I be taking part?
  • When will the results of the trial be known?
  • If I decide not to participate, what other treatment(s) will get?
  • What will happen if I decide to leave the trial before it finishes?
  • Will the results of the trial be published openly?
There are some much more practical questions to think about too, such as:
  • What extra tests or appointments are needed in addition to my standard care?
  • Will I need to take time off work?
  • How much time will I need to give to the trial?
  • If the trial includes new medicines, how will it be given to me?
  • Will I have to collect the medicine from the hospital, from my doctor or will it be sent through the post to me?
  • Will there be any help to cover the costs of my travel to participate in the trial?
  • Do you know if the treatment will have any side effects? If so, what are they?
  • Do you know if the treatments may have an affect on me physically or emotionally?
  • Who can I contact if I have questions or a problem?
  • Will they be available 24 hours a day?
  • How do I find out the results of the trial?