A new treatment goes through several phases. Each phase has a different purpose:
Learn more about the different phases of clinical trials.
Test if a new treatment is safe in people. Doctors also find the best way to give the treatment.
The goal of a Phase I trial is to:
Phase I trials usually include 15 to 30 patients who are divided into small groups. These groups are called cohorts. The first cohort receives a dose of the new drug. Doctors may collect blood or urine samples to measure drug levels in the patients.
If the first cohort does not have any severe side effects, then a new cohort receives a higher dose of the same drug. The dose increases with each new cohort until the doctors find the best dose for future testing. With each increasing dose, doctors test each patient to see if he or she is responding to the protocol. If the doctors find that the treatment is safe, then it will move forward to be studied in a Phase II trial.
The average length of a phase I clinical trial can be relatively short due to it being an introductory phase.
Test if a new treatment works in one type of cancer.
Fewer than 100 patients usually join a Phase II trial. Even though the main goal is to see if the treatment works, doctors still closely watch patients’ side effects. If the new treatment works, doctors may go on to study it in a Phase III trial.
The average length of a phase II clinical trial can be anywhere between less than a year to up to two years.
Test if a new treatment is better than standard treatment.
Phase III trials may include hundreds to thousands of patients around the country or world. Each patient enrolled in a Phase III clinical trial has a chance of being in one of the following groups:
How are patients put into groups? A computer decides which patients are in the control group and which patients are in the study group. Patients have a chance of being in either group. The patient and doctor do not decide. It is random and due to chance alone. This helps to avoid bias in the clinical trial. (Bias happens when human choices affect a study’s results.)
Would my doctor know which group I am in? In single blind studies, patients do not know whether they are in the control or study group, but the doctor does. In double blind studies, neither the patients nor the doctors know which patients are in each group. (In case of an emergency, doctors can find this information in the study file.)
Would I be given a placebo? A placebo is something that looks like medicine, but is not. If a placebo is used, it is given together with the best standard treatment. This allows doctors to compare standard treatment alone to standard treatment with a new drug. If there isn’t a standard treatment, then the placebo may be given alone, but this is not common in cancer trials.
After the Phase III trial, the FDA reviews the clinical trial results to make sure the treatment is safe and effective for people to use. The FDA decides whether to approve the treatment so that it is available for all patients.
The average length of a phase III clinical trial can vary, ranging from one to four years or longer.
Find more information about long-term side effects.
In Phase IV trials, doctors study treatments that the FDA has already approved. The goal of Phase IV trials is to continue studying side effects of a new treatment. The average length of a phase IV clinical trial is usually shorter than phase III so typically less than four years.