An independent group, or groups, oversee the trial to make sure it continues to be as safe as possible for the people taking part. They check how the trial is being run and that the trial plan (protocol) is being followed. They also monitor the information being collected to check the safety of the trial and how well treatment is working. They can stop a trial if it is causing harm to a person. For example, they could stop a trial if people are having severe side effects. They will also stop a trial early if the results show the new treatment is much better than standard treatment. This means doctors can start using the new treatment instead of the standard treatment.