What is a clinical trial?

A clinical trial is a carefully designed investigation of the effects of a test or treatment.

​What are clinical trials and what do they look at?

These medical research studies involve people and look at:

  • Risks and causes – how genetics, lifestyle and other factors can increase people’s risk of cancer
  • Preventing cancer – using drugs, vitamins or diet to reduce risk
  • Screening – for people at higher than average risk, or for the general population
  • Diagnosing cancer: new tests or scans
  • Treatments – new drugs or combinations, new types and methods of giving treatment
  • Controlling symptoms or side effects – new drugs or complementary therapies


  • Screening: to find ways of detecting cancer at an earlier stage
  • Diagnosing cancer: looking at new tests or scans that can help detect cancer in a better way


  • Treatment with new drugs or combinations of drugs, or new ways of giving drug treatments, surgery or radiotherapy
  • A new treatment may be compared with an older and more accepted treatment to find out which works better
  • The question may be “Is the treatment being given in the best way?” For example, comparing how frequently drugs are given – once a week or once a month
  • Monitoring the progress of treatment

Supportive care

  • Controlling symptoms, such as pain, nausea or shortness of breath. For example, a trial may look at new drugs or complementary therapies
  • The researcher may want to discover how best to provide support by finding out how treatment affects your everyday life and activities


  • To help learn more about the role genes play in cancer

Preventing cancer

  • These trials are conducted with healthy people who have not had cancer. For example, they may look at drugs, vitamins, foods to reduce risk, etc.

Researchers use different methods to answer different questions – for example randomised trials or questionnaires and interviews.