What is a clinical trial?
Clinical trials are research studies in which people help doctors find ways to
improve health and cancer care. Each study tries to answer scientific questions and
to find better ways to prevent, diagnose, or treat cancer.
Why are there clinical trials?
A clinical trial is one of the final stages of a long and careful
cancer research process. Studies are done with people who volunteer to find out whether
promising approaches to cancer prevention, diagnosis, and treatment are safe and
What are the different types of clinical trials?
- Treatment Trials test new treatments (like a new cancer drug, new approaches
to surgery or radiation therapy, new combinations of treatments, or new methods such as
- Prevention Trials test new approaches, such as medicines, vitamins, minerals,
or other supplements that doctors believe may lower the risk of a certain type of
cancer. These trials look for the best way to prevent cancer in people who have never
had cancer or to prevent cancer from coming back or a new cancer occuring in people who
have already had cancer.
- Screening Trials test the best way to find cancer, especially in its early stages.
- Quality of Life Trials (also called Supportive Care trials) explore ways to improve
comfort and quality of life for cancer patients.
What are the phases of clinical trials?
Most clinical research that involves the testing of a new drug progresses in an
orderly series of steps, called phases. This allows researchers to ask and answer
questions in a way that results in reliable information about the drug and protects the
patients. Clinical trials are usually classified into one of three phases:
- Phase I trials: These first studies in people evaluate how a new drug should
be given (by mouth, injected into the blood, or injected into the muscle), how often,
and what dose is safe. A Phase I trial usually enrolls only a small number of patients,
sometimes as few as a dozen.
- Phase II trials: A phase II trial continues to test the safety of the drug,
and begins to evaluate how well the new drug works. Phase II studies usually focus on a
particular type of cancer.
- Phase III trials: These studies test a new drug, a new combination of drugs,
or a new surgical procedure in comparison to the current standard for treatment. A
participant will usually be assigned to the standard treatment group or the new
treatment group at random (called randomization). Phase III trials often enroll large
numbers of people and may be conducted at many doctors' offices, clinics, and cancer
For more information, please see the National cancer Institute's brochure,
Taking Part in Clinical Trials: Cancer Prevention Studies.
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