Phase I trials are the first step in testing a new treatment in human participants. There are many unanswered questions about a new treatment so Phase I trials are typically carried out on a small number of participants who have not responded well to standard treatment. Researchers will be looking at such things as what is the best dosage, how often to give the treatment, whether there are any side-effects and how the body processes the treatment (e.g. digests, circulates and eliminates the treatment).

Phase II trials begin to focus on the treatments effectiveness in the specific type of cancer. Researchers look at such things as will the treatment shrink a tumour or will it improve blood test results. The researchers will also continue to evaluate the treatments side effects.

 

 

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Phase III trials compare the results of participants taking the new treatment with the results of participants receiving the standard treatment. Phase III studies typically compare which group lives longer and have fewer side-effects. Participants are randomly assigned to the new treatment or to the standard treatment. Researchers assign the participants by chance to one of the treatment groups. This process is called randomization and it helps make sure that accurate and true results are obtained.

When participants know what group they were randomized to it may change the way they react or feel, so it is important that the participant not know what group they were randomized to. This is called a blinded study. In a double blind study neither the participant nor the physician knows which treatment the participant is receiving. This helps prevent any personal bias from influencing the study results.

Phase IV trials are typically known as post approval trials. They are often conducted in order to obtain more information on long term side-effects or in order to offer access to not yet funded treatments.