Trial terms glossary

Breast cancer

Glossary of trial terms



A treatment given in addition to the main form of treatment (e.g. chemotherapy in addition to surgery) that aims to delay or prevent recurring disease by destroying possible remaining cancer cells.


A treatment group in a clinical trial. All patients in the group receive the same treatment or intervention. A trial with a treatment and a control group would be called 2-armed.Some trials may have three or more arms.

Blinded trial

A trial in which participants don't know whether they're in the intervention group or the control group. This prevents people from reporting benefits because they believe they're receiving a new treatment.

Controlled trials

Trials designed to compare a new treatment against the standard existing treatment. One group (the trial or intervention group) are given the new treatment, while the other group (the control group) are given the standard existing treatment. If there is no existing treatment, the control group might be given a 'placebo'.

Double-blind trials

In these trials neither the patient nor the doctor knows which group the patient is in. This prevents the researcher's knowledge, expectations or possible biases from influencing their observations.


Endpoints describe the overall goals of the study. They often include things like overall survival, tumour response or quality of life.


The 'line' of treatment describes the order it's used in. A first-line treatment is the initial treatment given. A second-line treatment is given when a first-line treatment doesn't work.

Open-label trial

A study where participants and researchers are aware of which treatment has been assigned. The opposite to a double-blind trial.


An inactive substance which is designed to look like the drug being tested, but does not have any effects. By comparing the effects of a treatment to the effects of a placebo, researchers can find out how effective the new treatment really is. Those who receive a placebo will still receive the current best evidence-based treatment that is normally provided to patients.

Principal investigator

The scientist or doctor in charge of the clinical trial.


A plan that outlines the design, objectives and methods of a clinical trial.

Randomised trial

A trials in which patients are randomly allocated to a group or arm of the trial by a computer to ensure the treatment and control groups have a similar mix of people of different ages, sexes and states of health.

Serious adverse rvent

An unfavourable change in the health status of a clinical trial participant during the course of the trial or in a period afterwards. This may require hospitalisation, be life-threatening or result in incapacity or death and may or may not be due to the treatment being studied.

Standard treatment

The current best evidence-based treatment that is normally provided for people with a particular condition.

Treatment group

The group of patients receiving the new treatment in a clinical trial.