Comprehensive Cancer Care Services

Phases of Clinical Trials

Before a treatment can become considered standard treatment, it must go through 3 or 4 clinical trial phases. It is not necessary to take part in all phases. The following is a brief explanation of each phase:

  • Phase 0
    Even though phase 0 studies are done in humans, this type of study is not much like the other phases of clinical trials. It is included here because some cancer patients may be asked to take part in these kinds of studies in the future.
    Phase 0 studies are exploratory studies that often use only a few small doses of a new drug in each patient. They test to find out whether the drug reaches the tumor, how the drug acts in the human body, and how cancer cells respond to the drug. The patients in these studies must have extra biopsies, scans, and blood samples. The biggest difference between phase 0 and the later phases of clinical trials is that there is no chance the volunteer will be helped by taking part in a phase 0 trial. Because drug doses are low, there is also less risk to the patient in phase 0 studies compared with phase I studies.
    Phase 0 studies help researchers find out which drugs do not do what they are expected to do. If there are problems with the way the drug is absorbed or acts in the body, this should become clear very quickly in a phase 0 trial. This process may help avoid the delay and expense of finding out years later in phase II or even phase III clinical trials that the drug doesn’t act as it was expected to based on lab studies.
    Phase 0 studies are not yet being used widely, and there are some drugs for which they would not be helpful. Phase 0 studies are very small, mostly with fewer than 20 people. They are not a required part of testing a new drug, but are part of an effort to speed up and streamline the process.
  • Phase I
    These studies are usually the first studies of a new drug that involve people. Although the treatment has been tested in lab and animal studies, the side effects in people can’t always be predicted. For this reason, these studies usually include a small number of people (15 to 50) and may be reserved for those who do not have other good treatment options. Often, people with different types of cancer are eligible for the same study.
    The main reasons for doing phase I studies are to find out the highest dose of the new treatment that can be given safely without serious side effects. They also help to decide on the best way to give the new treatment. The first few people in the study often get a low dose of the treatment and are watched very closely. If there are only minor side effects, the next few patients may get a higher dose. This process continues until doctors find the dose that is most likely to work while having an acceptable level of side effects.
    Safety is the main concern at this point because this is usually the first time the treatment has been used in people. Doctors keep a close eye on how the people in the study are doing. They watch for any serious side effects. Because of the small size of phase I studies, rare side effects may not be seen until later. Special tests, such as blood tests to measure levels of the drug in the body at certain time points, are often a part of these clinical trials. Some studies may require time in a hospital. Placebos (sham or inactive treatments) are not part of phase I trials.
  • Phase II
    If a new treatment is found to be reasonably safe in phase I clinical trials, the treatment can then be tested in a phase II clinical trial to see if it works the way researchers think it will.
    Usually, a group of 25 to 100 patients with the same type of cancer gets the new treatment in a phase II study. They are treated using the dose and method found to be most safe and effective in phase I studies. In a typical phase II clinical trial, all the volunteers usually get the same dose, and no placebo is used.
    But some phase II studies do randomly assign participants to 1 of 2 treatment groups, much like what is done in phase III trials (see below). These groups may get different doses or get the treatment in different ways to see which provides the best balance of safety and effectiveness.
    Doctors look for some evidence that the treatment works. The type of benefit or response they look for depends on the goals of the clinical trial. This may mean the cancer shrinks or disappears. Or it might mean there is an extended period of time where the cancer does not get any bigger, or there is a longer time before a cancer comes back. In some studies the benefit may be an improved quality of life. Many studies look to see if people getting the new treatment live longer than they would have been expected to without the treatment.
    If a certain percentage of the patients benefit from the treatment, and the side effects aren’t too bad, the treatment is allowed to go on to a phase III clinical trial. Along with watching for responses, the research team keeps looking for any side effects. Larger numbers of patients get the treatment in phase II studies, so there is a better chance that less common side effects may be seen.
  • Phase III
    Treatments that have been shown to work in phase II studies usually must successfully go through one more stage of testing before they are approved for general use. Phase III clinical trials compare the safety and effectiveness of the new treatment against the current standard treatment.
    Phase III clinical trials usually have a large number of patients, at least several hundred. These studies are often done in many places across the country (or even around the world) at the same time.
    Because doctors do not yet know which treatment is better, patients are often chosen at random, (called randomized) to get either the standard treatment or the new treatment. When possible, neither the doctor nor the patient knows which of the treatments the patient is getting. This type of study is called a double-blind study. Randomization and blinding are discussed in more detail later on.
    As with other studies, patients in phase III clinical trials are watched closely for side effects, and treatment is stopped if they are too bad. Placebos may be used in some phase III studies, but they are never used alone if there is already a treatment available that works.
  • Phase IV
    Even after testing a new medicine on thousands of people, the full effects of the treatment may not be known. Some questions often still need to be answered. For example, a drug may get FDA approval based on the fact that it was shown to reduce the risk of cancer recurrence. But does this mean that those who get it are more likely to live longer? Are there rare side effects that haven’t been seen yet, or side effects that only show up after a person has taken the drug for a long time? These types of questions may take many years to answer fully, and may not be critical for getting a medicine to market. They are often addressed in what are known as phase IV clinical trials.
    Phase IV studies look at drugs that have already been approved by the FDA. The drugs are already available for doctors to prescribe for patients, but these studies are still needed to answer important questions.
    When thinking about taking part in a phase IV trial, you should know that the drug has already been approved for use. You do not need to enroll in the study to get the medicine. At the same time, the care you would get in these types of studies often is very much like what you could expect if you were to get the treatment outside of a clinical trial. You should be reassured that in taking part you would be getting a form of treatment that has already been studied a lot and that you would be doing a service to future patients.

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