How clinical trials are monitored

The data monitoring committee

A data monitoring committee (DMC) is usually set up before a trial starts. It looks at the safety and design of the trial. The DMC regularly checks the progress of the trial at specific times set out in the protocol.

They look at things such as:

• how many patients have agreed to take part

• how many patients have withdrawn from the trial

• any side effects people have had

• patient feedback about the trial

• any results so far

The DMC then recommend that the trial:

• continues as it is

• continues with some changes

• stops early

• runs for longer

The ethics committee

The ethics committee also keeps an eye on how the trial is going. The research team must tell the committee if patients in the trial have any unexpected side effects.

If the ethics committee needs to, they can:

• stop the trial completely, earlier than planned

• stop the trial temporarily while they decide the best thing to do

• ask the research team to change the trial plan (the protocol)

• ask the research team to update the patient information sheet and consent form

Stopping trials early

Stopping a trial early means that the trial will close to recruitment. Trials can be closed early if:

• it’s clear that the trial treatment is obviously much better than standard treatment

• the trial treatment is much worse than the standard treatment

• people are having severe side effects from treatment

Researchers don't like to close trials early unless there is very strong evidence that one group of patients is doing much better than the other. Closing a trial early can make it difficult to interpret the results. Sometimes results may seem better for one treatment over another in the short term. This may not be the case in the long term.

A trial can also close early if it is recruiting patients much more slowly than expected. The funding organisation may decide that the trial is recruiting so slowly that it will take too long to come up with any results. In that case, it may not be a good use of funds. And it may not be ethical to carry on entering patients into a trial that is not going to decide anything in the long run.

Running trials for longer

The data monitoring committee may suggest that the trial runs for longer than planned. They may do this if they think there is a possibility the trial can prove something useful, but that more patients are needed to get enough results.

Long term results

Researchers usually continue to collect information about patients who have taken part in a trial after they finish treatment. Sometimes they do this for several years. This allows the research team to:

• see how well treatments work in the long term

• find out about any long term side effects