• Learn about cancer
• Cancers at a glance
• Research highlights
• About cancer research
  • What is 'research'?
  • The scientific method
  • Different areas of research
    • Basic research
    • Translational research
    • Clinical research
      • Phase 1 trials
      • Phase 2 trials
      • Phase 3 clinical trials
      • Phase 4 clinical trials
    • Behavioural and population research
    • Psychosocial research
• Understanding 'risk'
• Our history and achievements

Phase 4 clinical trials

Phase 4 trials look at the long-term safety and benefits of a treatment. It continues to study the treatment once it has been approved for use and doctors are able to give it to patients routinely.

Phase 4 studies are useful for gathering information on any side effects that may have been missed in the earlier trials. Because researchers are looking at even more people, they are more likely to spot unusual side effects that only happen in a small number of people.

If you want to find out even more about phase 4 clinical trials, have a look at the ‘Understanding clinical trials’ section of our CancerHelp UK website.