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What are clinical trials?


A Clinical Trial is any medical research study that involves people. Clinical trials are the only reliable way to test if a new treatment or procedure:

Is safe
Has side effects
Works better than current treatments/procedures
Helps patients feel better

We are making real progress in improving the care and treatment of patients with cancer. However, we need to continue to develop new drugs so that we can help even more people with cancer.

Trials are usually carried out in a stepped/phased process.

Phase I

6-30 patients
Small patient groups

To test:

dose safety
side effects

Note:  Patients on Phase I trials often have advanced cancer and have received all possible current treatments

Phase II

20-150 patients

To test:

effectiveness balanced to side effects
if the new treatment works better for particular cancer

Phase III

100s-1000s of patients

To test:

new vs. current treatment (might become new treatment)
may include ‘Quality of life’ study

Phase IV

>1000 patients

To find out more about the side effects, long term risks and benefits of current treatment


One may find that along with the phased trial, the trial has an additional category:


Randomised trials

A randomised trial involves patients being allocated at random to treatment groups in the trial. Patients are usually selected at random using a computer programme; therefore neither the patient nor the doctor will be able to influence the selection. It is important that comparison is made like with like between each treatment group, each group has to have a similar mix of people of different ages, sex and state of health.

Blind trials

A blind trial means that the patients are not told which treatment group they are in. If a patient knows which treatment they are receiving, it might influence their reaction or how they report the symptoms.

If a trial is a double blind, this means that neither the patient nor the doctors treating them know who is receiving which treatment. As with the blind trial explanation above, this is to prevent possible influence from the doctor’s expectations.

To ensure the “blind” aspect of a trial, all treatments are made to look as similar as possible.

Controlled trials

Controlled trials compare different treatments; this is likely to be comparing a new treatment with a standard or usual treatment. The trial involves setting up two groups:

Trial/intervention group: this group is given the new treatment
Control group: this group is given the standard or usual treatment. Where there is no standard treatment, this group may be given a placebo

Comparing the results achieved by both groups is the only way researchers are able to reliably find out if a new treatment is more effective than the standard/usual treatment.

Charity appeal

Find out more about our £1m Charity appeal for the AcceleraTED cancer Treatment programme.