Clinical trial design

If you take part in a trial you may hear your research team use terms such as:

  • controlled trials
  • randomisation
  • placebo (inactive treatment)
  • blind trials.

In most controlled trials, one group of patients have the standard treatment for the cancer. The other group have the trial treatment which is being tested. The results are compared to see if there is any benefit from the new treatment and if the side effects are better or worse.

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

Sometimes when a new drug is being added to the standard treatment researchers use a placebo. A placebo is an inactive treatment that has no effect on the cancer but looks the same as the new drug being tested. One group gets the standard treatment plus the new drug while the other group gets the standard treatment plus a placebo. You will not know if you are getting the new drug or a placebo. This is called a blind trial.

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.

I took part in a clinical trial of a new chemotherapy drug. I'd already had treatment so my progress was measured against the new one.

Ron, clinical trial participant


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

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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.

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