Phases

Clinical trials are divided into different steps, called phases. The earliest phases look at whether a treatment is safe and examine potential side effects. Later phases test whether a new treatment is more effective than existing treatment.

Phase 1 trials

A phase 1 trial is often the first time a new treatment is used on actual people, as opposed to animals or human cells. In certain instances, phase 1 trials may test already approved drugs to determine if improvements or new uses are possible.
A phase 1 trial explores:

Delivery methods and frequency of treatment
Safest dosage and the highest recommended dose
How the human body responds to the drug
Potential side effects

These trials can come with a higher degree of risk as compared to later phase trials.
Phase 1 trials tend to involve a small number of people with cancer who are not responding to standard treatment. In some cases, these trials may involve people with different types of cancer in efforts to assess the safety of a new treatment and determine best dosages.

Phase 2 trials

Phase 2 trials narrow focus to a specific type of cancer, using phase 1 results to guide dosage and frequency. At this phase, different treatment schedules may be tested.

A phase 2 trial aims to:

Test the effectiveness of a new drug on a specific type of cancer
Evaluate the safety of a new treatment and learn more about its effect on the body

Although treatments in phase 2 trials have been tested in phase 1 trials, there may still be unknown side effects.

Phase 2 trials are often larger than phase 1 trials. Up to 100 people may be participating.
In a phase 2 trial, a new treatment may be compared with an existing treatment that’s already in use, or with a placebo. If phase 2 trials show that a new treatment is as effective as an existing treatment, or more effective, the new treatment proceeds to phase 3.

Phase 3 trials

Promising new treatments identified in phase 2 trials are compared to the best available treatment (standard treatment) in phase 3. These trials involve hundreds to thousands of participants in numerous locations. In some cases, participants may not have received treatment previously.

A phase 3 trial aims to compare the new treatment to standard treatment based on:

Overall effectiveness, including quality of life considerations and impact on survival
Side effects

To ensure the accuracy of results, phase 3 trials often use randomized groups of participants. In these cases, one group receives the new treatment and one group receives standard treatment.

If findings show that the new treatment is better than existing standard treatment, the new treatment may become the new standard treatment. To be considered, the new drug would have to be approved by Health Canada. From there a review board, called the pan-Canadian Drug Oncology Review (pCODR), will recommend whether or not the drug will be publicly funded and this will inform related decisions at the provincial and territorial levels. This process is different in Quebec, where INESSS (Institut national d’excellence en santé et en services sociaux) is responsible for determining public drug funding.

Phase 4 trials

Phase 4 trials are conducted after a drug has been approved for use by Health Canada. These trials probe for further information on the long-term risks and benefits of a new treatment. Phase 4 trials follow participants who have completed phase 3 trials.

These studies are not conducted on all new treatments.