Clinical trials are classified into one of three phases, each phase representing a different step in the testing of a new clinical treatment. Each step allows researchers to ask and answer important questions about the type of treatment and its effectiveness for patients.
Phase I trials determine the most appropriate way to give a new treatment. For example, should it be given by mouth, injected into the blood or injected into the muscle? These studies also evaluate what dose is safe and how often it should be used. A Phase I trial focuses on the safety of a treatment and generally involves only a small number of patients.
A Phase II trial determines how well a new treatment works. These trials test the safety of the treatment at a more advanced level than Phase I trials and evaluate the anti-cancer effect of the treatment.
Phase III trials are studies that compare a new treatment with current standard treatments. For example, a Phase III trial would evaluate whether a new drug is better than a drug that is currently being used to treat patients with the same condition. Similarly, a new surgical procedure may be investigated to determine whether it’s better than a surgical procedure that is the general standard of treatment. Phase III trials are only ever initiated if the results of Phase I and II trials show that the new treatment is safe and effective and likely to be as good as, or better than, the standard treatment. Phase III trials involve hundreds of patients, often from around the world.
Randomised control trials are where the treatment that a participant receives is chosen by random allocation (i.e. the decision about which treatment to give which patient is randomly selected, usually by computer). When a patient is ‘randomised’ it means that they have been randomly selected to receive either a particular treatment or intervention (i.e. a new drug) or placebo – a pill that contains no active ingredient.