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Types of clinical trials

Most clinical trials start with cancer research in a laboratory (laboratory-based), where scientists try to understand cancer at its most basic and deepest level. If a new approach seems promising in the laboratory, the next step may be to test it on animals. If the research continues to show positive results, the next step is to do clinical testing and have people participate.

The main types of clinical trials in the field of cancer research are:

Type of clinical trialDescription


Looks for ways to reduce the risk of developing cancer in healthy people who have not had cancer or people who are at a higher risk of developing a certain type of cancer. Researchers may also conduct prevention trials in people with a history of cancer to try to prevent it from coming back (recurring) or to reduce the chance of developing a new type of cancer.

Examples of prevention trials include:

  • drug or chemoprevention studies – studying certain drugs, vitamins, minerals or other supplements to see how useful they are at lowering cancer risk
  • action studies – studying lifestyle factors, such as exercising, quitting smoking or eating more vegetables and fruit, to see if these choices help prevent cancer

Screening and early detection

Tests or evaluates the best ways to find cancer early in people who do not have any signs or symptoms of cancer. Finding cancer early can often improve the results of treatment and increase the chances of survival. People who have a higher than average risk of developing a certain type of cancer or people who have been exposed to cancer-causing substances (such as tobacco) may be offered a chance to participate in a screening and early detection clinical trial.

Examples of screening and early detection trials include studying:

  • new medical imaging methods to find cancer early before it causes symptoms
  • laboratory tests to detect the presence of tumour markers associated with cancer in a person’s body
  • genetic tests to detect inherited gene mutations associated with cancer


Looks for better ways to diagnose or stage cancer.

Examples of diagnostic trials include studying:

  • new medical imaging methods to find cancer
  • laboratory tests to detect the presence of  tumour markers associated with cancer in a person’s body
  • sentinel lymph node biopsy to remove and sample a few lymph nodes to see if they contain cancer


Tests or evaluates new cancer treatments and usually compares new cancer treatments with ones that already exist (standard treatments). This is the most common type of clinical trial involving people with cancer.

Examples of treatments tested in clinical trials include:

  • surgery – testing new techniques and timing of surgical procedures
  • chemotherapy – testing existing drugs used for other types of cancers or testing new drugs, drug combinations, different dosages and schedules for taking the drugs
  • radiation therapy – testing new methods of delivering radiation or combining radiation with other cancer therapies
  • hormonal therapy – testing new ways to protect people with cancer from the effects of various hormones on cancer cell growth
  • biological therapy – testing new treatments to stimulate and restore the body’s own defences (immune system) against a particular type of cancer or to target specific molecules involved in cancer cell growth

Supportive care

Studies how to reduce the impact of cancer and improve comfort levels and quality of life for people with cancer and cancer survivors. These are also called quality of life trials.

Examples of supportive care trials include studying:

  • better ways to improve nutrition and prevent or manage nausea, fatigue, pain or other problems caused by cancer or its treatment
  • psychological and social problems related to cancer or its treatment and how to cope with these

Randomized clinical trials

Researchers conduct phase III and sometimes phase II clinical trials as randomized clinical trials. In these studies, the participant is randomly assigned to the experimental group (receiving the new, experimental treatment) or a control group (receiving standard treatment). This study design is ethical when it is not known which treatment is better.

Sometimes participants in the control group may be given a look-alike pill or an injection that does not contain any active drug (placebo). This study design is ethical if it is not known if there is benefit or risk from taking the experimental treatment.

People who participate in randomized clinical trials have an equal chance that they will be assigned to either the experimental or control group. A computer usually assigns random numbers to participants. The number a person is assigned will decide whether or not they are in the experimental or control group. The doctor who conducts the trial (principal investigator) does not decide whether a participant is in the control or experimental group.

Blinded clinical trials

Researchers may conduct clinical trials as blinded clinical trials. In these studies, the researcher knows if a participant is in the experimental group or a control group, but the participants do not know what group they are in. This is because if a person knows what treatment they are getting, it may affect their response. For example, those who know they are getting the experimental treatment might expect it to work better and report positive or hopeful signs because they want to believe they are getting well. This could throw off the results of the study.

In double-blinded studies, neither the participants nor the researchers know which treatment group participants are in or what treatment they are receiving. This study design is preferred as it prevents both the participant and the researchers from doing things that may bias the scientific results.


A description of the extent of cancer in the body, including the size of the tumour, whether there are cancer cells in the lymph nodes and whether the disease has spread from its original site to other parts of the body.

Stages are based on specific criteria for each type of cancer.

The process of determining the extent of cancer in the body based on exams and tests is called staging.


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Great progress has been made

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Some cancers, such as thyroid and testicular, have survival rates of over 90%. Other cancers, such as pancreatic, brain and esophageal, continue to have very low survival rates.

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