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 an 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 specific 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

Use of Placebos

Placebos are sometimes used in clinical trials to test whether the results of a drug are better than no treatment at all. In these cases, a placebo designed to look like the drug being tested, but without any of the active ingredients, is administered to some participants for the duration of the study.

If a placebo is used in a clinical trial, you will be informed before participating that patients will receive either the treatment being studied or the placebo, at random. Individual participants are not informed which they will receive. If you have any questions about the effects of placebos or the reasons behind their use, ask your doctor or the clinical trial investigator. Read More

Patient-Related Links

Find an Open Clinical Trial

Other Online Resources

News & Events

Head and Neck Clinical Trial


Trial Terminology

Control Group / n. – a group of participants receiving the standard of care or treatment or a placebo whose results will be used as a comparison against the results of the participant group receiving the investigational treatment.