There are many different types of trials, each designed to answer a particular research question. Some trials may investigate a new treatment for cancer, while others seek to discover the effectiveness of a novel screening method.

Clinical trials involve a series of steps, called phases. If a trial is successful in a particular phase, it is moved to the next. It usually takes three or four successful phases before a treatment is made available to the public. Participants who sign up for one phase of the trial do not have to participate in all phases.

Clinical trials are usually sponsored by a pharmaceutical company, a university, a clinic or a cancer research centre. In all phases, patients interact with a research team led by an individual doctor, known as the investigator or principal investigator. Sometimes, an individual physician will act as both investigator and sponsor. 

Phase I
•    Purpose: To find a safe dose, determine how the new treatment should be given and how it affects patients
•    Number of participants: 15-30 people

•    Learn more about Phase I clinical trials

Phase II
•    Purpose: To determine if the new treatment has an effect on a certain cancer and to see how the treatment affects patients
•    Number of participants: Less than 100 people
Phase III
•    Purpose: To compare the new treatment with the current standard treatment
•    Number of participants: From 100 to several thousand people
Phase IV
•    Purpose: To continue to assess the long-term safety and effectiveness of a new treatment
•    Number of participants: Several hundred to several thousand people