Clinical Trials Glossary



active ingredient

The drug being tested.

adjuvant therapy

Treatment that is added to increase the effectiveness of a primary treatment. In cancer, adjuvant treatment often refers to chemotherapy, hormonal or radiation therapy after surgery, which is aimed at killing any remaining cancer cells.

advanced cancer

Cancer that has metastasised (spread to a part of the body away from the original cancer) and is more difficult to treat.


Part of the body's immune system. Antibodies are proteins made by the blood in response to an invader (antigen) in the body. They help protect against viruses, bacteria and other foreign substances.


At the beginning of the trial, before treatment is started.


Human choices or other factors not related to the treatments being tested that affect a study's results.

blinded trial

A trial in which participants do not know which treatment they are getting.


A general term for abnormal cell growth and its uncontrolled spread.


The use of special (cytotoxic) drugs to treat cancer by killing cancer cells or slowing their growth.

clinical trial

A research study that tests new and better ways of improving health in people.

control treatment

The existing treatment that is being compared with the experimental treatment. The control is generally the best standard treatment available.

controlled trial

A controlled trial compares two or more treatments to discover which is best.

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The identification and naming of a person's disease.

double blind trial

A trial in which neither the patient nor their doctor knows what treatment the patient is receiving, to reduce bias.

eligibility criteria

Characteristics of the people for whom the trial is suitable.

ethics committee

A hospital committee that reviews the plan for a clinical trial to ensure it is safe and ethical.

experimental treatment

The new treatment being tested in the trial.

fact sheet

An information sheet for people in a trial that should explain everything they need to know about the trial and its treatment. Also known as a participant or subject information sheet.

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gene therapy

Treatment aimed at correcting or interfering with a genetic abnormality causing cancer.


A substance that has a specific effect on the way the body works. Hormones, which are made by glands, help to regulate and co-ordinate growth, metabolism and reproduction.

hormone therapy

Medical treatment using hormones.

informed consent form

The form a person signs to show that they understand the information they have been given about a trial and that they agree to take part.

informed decision-making (informed consent)

A process in which a patient makes a decision - about a clinical trial or treatment - after being given information that they fully understand and give their consent in writing.


A researcher in a clinical trial.

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medical oncologist

A doctor who specialises in treating cancer with drugs.


A process in which the results of a number of clinical trials assessing the same questions are summarised, compared and combined.


Also known as a secondary cancer. A cancer that has spread from another part of the body.


A doctor who specialises in the study and treatment of cancer.


The branch of medicine concerned with the study and treatment of cancer.

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palliative treatment

Support and treatment directed against the effects of the cancer, not against the cancer itself.

participant information sheet

An information sheet that explains everything a participant needs to know about the trial and treatment. Also known as a fact sheet.

peer review

A process in which independent experts check something. For example, ethics committees include peer review by getting independent experts to check all clinical trials before they can go ahead. Medical journals also have a peer review process, in which experts check articles before they are accepted for publication.


A dummy pill or injection, which looks like the new treatment being tested but contains no active ingredient.

prevention trial

Trials that test new approaches that doctors believe may lower the risk of getting cancer.

primary cancer

The original cancer. Cells from the primary cancer may break away and be carried to other parts of the body, where secondary cancers may form.


An action plan that describes what will be done in the study and why.

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quality of life

How a person is feeling and doing. Quality of life is often affected by cancer and its treatments.

radiation oncologist

A doctor who specialises in radiotherapy to treat cancer.


The use of radiation, usually x-rays or gamma rays, to kill cancer cells or injure them so they cannot grow and multiply. Radiotherapy treatment can also harm normal cells, but they are able to repair themselves.


A method used to prevent bias in research. A computer will be used to put patients into groups by chance, rather than the doctor choosing.

randomised controlled trial

A trial in which participants are randomly allocated to receive the new treatment or the standard treatment (the control).

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An organised program to identify disease, such as cancer, before symptoms appear.

screening trial

A trial that tests the best way to find cancer, especially in its earliest stages.

secondary cancer

Also called a metastasis. A tumour that has spread from the original site to another part of the body.

side effect

Unintended effects of a drug or treatment.


The extent of a cancer, and whether the disease has spread from an original site to other parts of the body.

standard treatment

The best treatment known, based on results of past research.

supportive treatment

Treatment directed against the effects of the cancer, not against the cancer itself.

surgical oncologist

A doctor who specialises in the surgical treatment of cancer.

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treatment trial

A trial that tests a new treatment.


A new or abnormal growth of tissue on or in the body.

The Cancer Council Western Australia acknowledges The Cancer Council New South Wales as the original source of this glossary. Reproduced from the Understanding Clinical Trials booklet with the kind permission of The Cancer Council New South Wales.

For a comprehensive dictionary of cancer terms please visit the US National Cancer Institute

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