Clinical trial design

If you take part in a trial you may hear terms such as:

  • controlled trials
  • placebo
  • randomisation
  • blind and double blind trials.

In most controlled trials, one group of patients will have the standard treatment for their cancer type. The other group will have the trial treatment which is being tested. The results are then compared to see which treatment works and if the side effects are worse or better.

Sometimes when there isn’t a standard treatment available, one of the groups is given a placebo treatment instead. This looks the same as the treatment being studied but it contains no medicine. It is also called an inactive treatment.

To decide who goes into each group in a fair way, a computer places patients into treatment groups. This is called randomisation.

You may not be told which treatment group you are in. This is called a blind trial. In some trials called double blind trials, neither the patient nor the doctor will know which treatment they are getting.

Trial design

With phase 2 or phase 3 trials, you may hear your research team use different words. These describe the different ways that trials are set up to give the best results.

They include:

  • controlled trials
  • randomised trials
  • placebo and blind trials.


Controlled trials

In most trials, one group of patients will have the trial treatment and one group will have the standard treatment. Groups are randomly selected (see ‘randomised trials’ below).

Sometimes, the standard treatment is to ‘watch and wait’. This is when you do not need to have any treatment, unless the cancer starts to develop or cause symptoms.

The people with cancer who are having the trial treatment are called the trial group. The people having the standard treatment are called the control group. The researchers will compare the results of the trial group against the control group.

Researchers compare the results of both groups to find out if:

  • there is any benefit from the new treatment
  • the side effects are better, worse or different.

If the trial group shows any improvement, the researchers also measure:

  • how much of the improvement is due to the new treatment
  • how much would have happened by chance.


Randomised trials

Some phase 2 and phase 3 trials are randomised, controlled trials. This means that a computer programme randomly (by chance) chooses the groups for each treatment.

The computer matches the different groups to make sure they are as similar as possible. For example, this means they will have a mix of people with similar ages, gender or state of health.

Everyone taking part will get a code number and will be put into to the different treatment groups randomly. They may get:

  • the new treatment
  • the standard treatment, and sometimes an inactive treatment (a placebo) with it.

When people are put into treatment groups by a computer, it avoids any bias. If doctors or researchers decide who should get which treatment, they could be influenced by what they already know. Without realising it, they may put people more likely to respond to a new treatment into that particular group. This would affect the results of the trial and make a treatment look better than it is.

Randomisation
Randomisation

View a large version

Read a description of this image


Placebo and blind trials

A placebo is an inactive treatment that looks the same as the drug or treatment that is being tested. But it does not act on the cancer.

It may be used when a new drug is added to a standard treatment. One group will get the standard treatment plus the new drug. The other group will get the standard treatment plus a placebo. If you are in this group, it does not mean you will not receive any treatment. The placebo is given along with the standard treatment.

You will not know if you are getting the trial treatment or a placebo. This is called a blind trial. Researchers compare the responses to the placebo and the treatment being tested to find out if it has any benefit.

In many trials, doctors do not know whether you are getting the placebo or the treatment being tested. These are called double-blind trials.

In an emergency, your doctor can find out this information from the trial co-ordinators or the pharmacy department at the hospital.

Blind trials or double-blind trials aim to reduce any bias. For example, knowing you are having a new treatment might make you feel more positive or negative. This could influence what you report to the researchers. Also, your doctor may judge your response differently if they know you are having a treatment that they feel positive about.

Back to What are clinical trials?