Who can take part in a clinical trial

This page tells you about the entry conditions for trials. There is information about

Entry conditions

Researchers call the entry conditions for trials 'eligibility criteria'. This is because the patients taking part have to be as similar as possible. That way, if one group does better than the other, the researchers can be sure it was due to a difference in treatment and not because they had cancer at a different stage for example.

Eligibility criteria are clearly written in the trial protocol. Common entry criteria include the categories listed on this page.

Type of cancer

Many trials are only open to people with a particular type of cancer. This is because doctors and researchers are usually trying to find out if a treatment works for a single type of cancer. Cancers are different and treatment that works for bladder cancer may not work for breast cancer.

Some trials are open to two cancers that respond to treatment in the same way, such as stomach cancer and food pipe (oesophageal) cancer. Some trials, particularly phase 1 trials may be open to people with different types of cancer.

Stage of cancer

Many phase 2 and 3 trials are only open to people with the a particular stage of cancer. The stage is worked out by looking at the size of a cancer and whether it has spread to the lymph nodes or to another part of the body.

Previous treatment

This is an important condition for trial entry. A trial protocol may say you can't enter if you've had (or haven't had) a particular type of treatment. Some trials say that you can't take part if you are having another treatment at the same time as being in the trial. Or the protocol may say you must have had a particular treatment  for example, surgery before a radiotherapy trial.


This is usually a very wide range for adult treatment trials. It is usually there to make sure everyone in the trial is over 18. There are specific trials for children.

Some adult trials have an upper age limit. This will be for treatments that are tough to get through, such as high dose chemotherapy trials. Sometimes trials look at treatment for older people so you may need to be older than 65 or 70 to take part. They may be looking at a less intensive alternative to the standard treatment for a particular cancer.

General health (performance status)

When describing a person's general health, trial protocols usually call it performance status. Doctors use a scale to grade how well you are. There are different versions, but the World Health Organisation scale is the most commonly used.

  • 0 – you are fully active, more or less as you were before your illness
  • 1 – you can't carry out heavy physical work, but can do anything else
  • 2 – you are up and about more than half the day. You can look after yourself, but can't work
  • 3 – you are in bed or a chair for more than half the day. You need help to look after yourself
  • 4 – you are in bed or a chair all the time and need complete care

Many trial protocols may say they are open to people who have particular performance status, for example 0–2.

Karnofsky performance status is another commonly used scale. It is similar to the WHO scale, but goes to up 100.

  • 100 – you don’t have any evidence of disease and feel well
  • 90 – you only have minor signs or symptoms but are able to carry on as normal
  • 80 – you have some signs or symptoms and it takes a bit of effort to carry on as normal
  • 70 – you are able to care for yourself but not able to carry on with all your normal activities or do active work
  • 60 – you need help from time to time but can mostly care for yourself
  • 50 – you need quite a lot of help to care for yourself
  • 40 – you always need help to care for yourself
  • 30 – you are disabled and may need to stay in hospital
  • 20 – you are ill, in hospital and need a lot of treatment
  • 10 – you are very ill and unlikely to recover

The Lansky scale is used for children.

  • 100 – the child is fully active, normal
  • 90 – child has minor restrictions in strenuous physical activity
  • 80 – active, but tires more quickly than usual
  • 70 – can't play as energetically as normal and spends less time than usual in play activity
  • 60 – up and around, but active play is minimal – keeps busy by being involved in quieter activities
  • 50 – needs to lie down for much of the day but gets dressed  doesn't actively play but takes part in quiet play and activities
  • 40  mainly in bed but takes part in quiet activities
  • 30  can't get out of bed and needs help even for quiet play
  • 20  sleeps often and play is completely limited to very passive activities
  • 10  doesn't play and doesn't get out of bed
  •  doesn't respond at all

Other medical conditions and life expectancy

A few trials (usually those for an early stage of cancer) say that patients must have a life expectancy of more than a particular number of years  for example, 5 or 10. This is really a way of excluding people with other life threatening conditions, such as severe heart problems.

It seems harsh to use life expectancy to exclude people from a trial. But researchers won't get the results they need if a large proportion of their trial patients die of something else before the trial of the cancer treatment ends.

You may not be able to take part in a trial if you have a particular illness, even if it isn't life threatening. For example, if you have a heart condition, you may not be able to join a trial testing a drug that could have heart related side effects. Again, this seems hard, but the researchers may not be able to sort out the effects of the drug from the effects of your heart condition. And they will be worried about possibly putting you at risk of harm.

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