What is a clinical trial?

Medical research studies involving people are called clinical trials. This page tells you about what clinical trials can look at, what they aim to find out and different types of trials.

Clinical trials can look at

  • Risks and causes – how genetics, lifestyle and other factors can increase people's risk of cancer
  • Preventing cancer – using drugs or lifestyle changes 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 of drugs, new ways of giving treatment and new types of treatment
  • Controlling symptoms or side effects – new drugs or complementary therapies
  • Support and information for people with cancer

The aim of clinical trials

Trials aim to find out if a new treatment or procedure

  • Is safe
  • Has side effects
  • Works better than the currently used treatment
  • Helps you feel better

New treatments have to be thoroughly tested. For example, a new drug is investigated first in the laboratory. If it looks promising, it is carefully studied in people.

Different types of trials

There are 3 main phases of clinical trials – phase 1, 2 and 3. Some trials cover more than one phase. There are also phase 4 trials. These are carried out after a drug has been licensed – they collect information about side effects, safety and the long term risks and benefits of a drug. And some trials have an earlier stage called phase 0.

Usually, a new treatment has to go through a few phase 3 clinical trials before doctors are confident enough to accept it as the new standard treatment. One good trial result could happen by chance or because a trial  was not very well designed. This is not likely if several trials have the same results.

Not all clinical trials will result in new and better treatment. Some will discover that the treatment being tested does not work. Or that it has side effects that are much worse than with existing treatments. But this information is also useful for researchers and doctors, and in the end for patients.

Researchers may look at the impact a treatment has on you – for example, how often you have to travel to the hospital. Studies of impact and side effects are sometimes called quality of life studies. Most well planned trials include a quality of life study.

Questions about clinical trials?

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