Skip the primary navigation if you do not want to read it as the next section.
Skip the main content if you do not want to read it as the next section.
Trials go through several stages or phases...
Phase I
Phase I trials are to find out whether a new treatment has any effect at all on a particular cancer. Before the treatment is tried on patients, there will already be some evidence that it works against cancer in animals or in the laboratory.
Because the treatments are experimental and no-one knows whether they will work, Phase I trials always involve volunteers for whom there is no other treatment available.
Phase II
If a new treatment seems to have had some effect in a Phase I trial, it will be offered to other patients to see if it is worth developing further.
Phase II trials often need patients whose cancer can be measured (by examination, x-ray, CT or MRI scanning), so that the effects of the treatment can also be measured. For example if the cancer shrinks at least a certain amount (30% in its longest dimension), this is called a partial response. If it disappears completely, it is a complete response.
Phase II trials normally involve between 12 and 40 patients.
Phase III
Phase III trials directly compare the new treatment with the standard treatment. In most trials, half the patients get the new treatment, and the other half get the standard treatment.
If the new treatment proves to be better than the standard one, the new treatment becomes the standard treatment.
In some trials, more than one new treatment is tested.
We need to be sure that the result of each trial is genuine, and has not happened by chance. This is why Phase III trials are large (usually involving hundreds or thousands of patients) and randomised.
Randomised means that no-one can choose who gets the new treatment and who gets the standard one. Instead, patients are allocated randomly to one of the groups. This may be done by computer, but other methods are also used. By making the study randomised, no-one can influence the result.
