Before a new treatment can become part of standard treatment it
needs to go through a series of testing in what are called 'phases'. Following on from trials
using animals, the main aim of early phase trials is to test if the
treatment is safe for humans. Later phase trials investigate if the
treatment is more effective than the currently available standard
treatment. You may be asked to participate in any one of these
phases of testing if you decide to take part in a clinical
Phase 0 trials
Phase 0 trials are the first-in-human studies for drugs that
have been previously tested in animals. Usually a single drug dose
is given to 10-15 people to gather preliminary data on how the drug
is metabolised and what effect the drug has on the body. The dose
of drug given is below what is thought to have a therapeutic
Phase 1 trials
These are the first tests of a treatment in humans and involve
approximately 15-30 people. They aim to see if the trial treatment
is safe and to find the best dose. The research team notes major
and minor side effects. This helps researchers to work out the best
dose and the best way to give the trial treatment.
Phase 1 trials are usually only suitable for people with
incurable cancer who have had all the known effective treatments
for their cancer. People take part in these trials in the hope that
the treatment may extend their life or improve their quality of
life. Most often though, the reason to enter Phase 1 trials is to
help people with cancer in the future.
If a Phase 1 trial shows that the new treatment is safe it will
go on to Phase 2 testing.
Phase 2 trials
Phase 2 trials usually involve less than 100 people. The trials
aim to see how well the new treatment works against cancer and to
monitor for side effects.
Phase 2 trials generally involve people who have already had
cancer treatment. The chance of the treatment being tested in a
Phase 2 trial being effective depends on the type and extent of the
cancer and its response to previous treatment.
If the new treatment shows promising effects (efficacy) against
cancer and is safe then it is tested in Phase 3 trials.
Phase 3 trials
Phase 3 trials involve from hundreds to thousands of people. The
trials are usually conducted through doctors' offices, hospital
clinics and cancer centres around the country or even around the
world. They aim to test if the new treatment (the intervention
treatment) is better than the current best standard treatment. They
test treatments in real life settings, not the controlled
circumstances under which Phase 1 and 2 trials are usually
Participants in Phase 3 trials are put in either the new
treatment group or the standard treatment group at random. People
in the trial are monitored carefully to see the effect of the
treatment on the cancer, and on the length and quality of
If the new treatment works better, it may become the new
standard treatment. In general, the new treatment needs to go
through more than one Phase 3 trial for the treatment results to be
Phase 4 trials
'Phase 4 trial' refers to the long-term monitoring that
sometimes occurs after a drug has been licensed for use and put on
the market. Phase 4 trials are to assess any long-term side effects
of a new treatment. There are very few Phase 4 trials.