What are clinical trials?

What can clinical trials find out? 

Clinical trials can be used in a variety of settings. They can be used to: 

  • Find out if we can prevent illnesses by testing a new vaccine treatment 
  • Improve detection or diagnosis of illnesses by testing a method of scanning  or blood test 
  • Improve the current treatment of cancer by testing new or existing treatments. This applies to both medicines and radiotherapy treatments
  • Find out how best to provide psychological support to patients and carers  
  • Find out how people can control their symptoms and/or improve their quality of life

Phases of clinical trials

All new treatments are tested through a series of clinical trial phases to assess whether the treatments are safe and whether they work. A new treatment must pass through all the different stages of clinical trials in order to become standard.

All phases of clinical trials are carried out according to a strict set of rules (called a protocol), to ensure they are safe and measure the right things in the right way. They go through robust checks, from research ethics committees and other regulatory bodies (for example the Medicines and Healthcare products Regulatory Agency, the MHRA), as well as from The Christie's own Research and Development Department, before the clinical trial can begin.

Phase 1 clinical trials involve testing new drugs, often for the first time, in a small group of patients. These trials help doctors find out:

  • If a new drug is safe
  • If it has any side effects
  • How much of the drug can be given safely, and how often

These trials may be offered to patients with advanced cancers who have already exhausted other standard treatment options.

Phase 1 clinical trials also involve experimental drugs which target particular genetic faults and you may be asked if you want to be tested for one of these genetic faults. If your cancer appears to have one of these faulty genes, you may be invited to take part in an experimental therapy trial, either before or after receiving standard therapies.

The Christie has a dedicated experimental cancer medicines centre

Phase 2 studies are larger than phase 1 studies and aim to find out:

  • How the new medicine works in specific types of cancer
  • If there are any side effects and how to manage them
  • What is the best dose to use

In a phase 2 trial a new treatment may be compared with another treatment already in use, or with a dummy drug (placebo).

Phase 3 trials compare new treatments (which have passed through phase 1 and phase 2 trials) with the best currently available treatment. These trials normally last for a year or longer and take place in many different hospitals and countries at the same time. These studies also have a very large number of patients.

These trials may compare:

  • The new treatment with the standard treatment
  • Different doses or ways of giving a standard treatment
  • A new way of giving radiotherapy with the standard way

Phase 4 trials take place only when a new treatment has passed through stages 1-3, has been proven to work and has been given a marketing licence. Phase 4 trials look at the safety, side effects and effectiveness of the medicine while it is being used in daily practice. Not all medicines will require a phase 4 study.

Types of clinical trials

Not all trials will be designed in the same way. These are the most common types of clinical trial designs:  

Many researchers design trials as randomised controlled trials (RCTs) to ensure a trial is not open to bias.

In a RCT, patients receive one of at least two treatment ‘arms’. Neither the patient nor the doctor can choose which treatment will be allocated. There is normally a 50/50 chance of being allocated to either arm.

Each treatment arm will be balanced in terms of age, gender, disease stage etc. This ensures that, as far as possible, the only difference between the groups is the treatment they receive. At the end of the study, researchers can then be confident that any differences in outcome between the groups is due to the treatment. 

A blind trial is a type of clinical trial where the patient taking part does not know which treatment they are having. They could be receiving either the new medication or the standard treatment. The patient will not know which treatment they are having as the two methods for administering the treatment will be identical.

A double blind trial is when neither the doctor nor the patient knows which treatment the patient is receiving. These trials are designed to prevent bias affecting the trial results.

A code is given to the research team each time the patient is due medication and this code will reflect a treatment that the patient should receive. For safety reasons, this code can be broken at any time by the medical team to identify which treatment the patient is receiving.



Last updated: August 2019