Clinical trials are essential to providing the scientific data required to determine whether new drugs, diagnostics or procedures are both safe and effective when used to diagnose and treat people.

Carefully conducted clinical trials are performed in human volunteers to provide answers to important questions. Every new treatment is usually tested in three phases of clinical trials before regulatory agencies consider it safe and effective.

Terms used in clinical trials

Blind and double-blind

In a blinded clinical trial, the patient is not told whether they are receiving the active drug or another treatment/placebo. When neither the patient nor the investigators know to which group they have been assigned the study is double-blind. The blinding of trials is performed to try to avoid bias.

Placebo-controlled

A descriptive term for a clinical study in which one group of patients (the "control" group) receives an inactive substance, or placebo, while the drug being evaluated is given to another group. Placebo-controlled trials are rarely used for cancer treatments, where a new treatment is more likely to be compared with the existing standard-of-care treatment.

Endpoints/outcomes

Endpoints, set and defined in advance of the clinical trial, describe and define the goal(s) of the study. Examples of endpoints (which vary depending on the type and phase of trial) include overall survival, toxicity, tumour response, and quality of life measures.

Open-label

A descriptive term for a clinical study in which both investigators and patients are aware of what treatment has been assigned, i.e. the study is not blinded.

Randomised

A descriptive term for a clinical study in which patients are randomly assigned to one of two or more treatment arms of the study.

Adjuvant

A treatment given in addition to the main form of treatment (e.g. chemotherapy given immediately after surgery) that aims to enhance its efficacy, for example by delaying or preventing recurrent disease by destroying any remaining cancer cells left in the body following surgery.