Phases of Clinical Trials
Development of new anticancer agents and treatment strategies occurs in four
phases. Each phase is designed to determine specific information about the
potential new treatment such as its risks, safety and effectiveness compared to
standard therapy. The hope is that the new therapy will be an improvement over
the previous standard therapy.
Phase I Trials:
This phase is probably the most important step in the development of a new drug
or therapy. These trials usually involve a small number of patients for whom
other standard therapies have failed or no known alternative therapy is
available. Phase I therapy may produce anti-cancer effects and a small number of
patients may benefit. However, the primary goals of this phase are to determine
anticancer activity in humans, the maximum tolerated dose of the treatment, the
manner in which the drug works in the body, the toxic side effects related to
different doses and whether toxic side effects are reversible. Upon completion
of phase I trials, the information that has been gathered is used to begin phase
II trials.
Phase II Trials:
Once the information is gathered and analyzed from phase I trials, phase II
trials are designed to determine the effectiveness of the treatment in a
specific patient population at the dose and schedules determined in phase I.
These trials usually require a slightly higher number of patients than phase I
trials. This number may increase depending on the number of responses as the
phase II trial progresses. Drugs or therapies that are shown to be active in
phase II trials may become standard treatment or be further evaluated for
effectiveness in phase III trials.
Phase III Trials:
Phase III trials compare a new drug or therapy with a standard therapy in a
randomized and controlled manner in order to determine proof of effectiveness.
Phase III trials require a large number of patients to measure the statistical
validity of the results because patient age, sex, race, and other unknown
factors could affect the results. To obtain an adequate number of patients,
several physicians (investigators) from different institutions typically
participate in phase III clinical trials.
Phase IV Trials:
Once the drug or treatment becomes part of standard therapy, the manufacturer of
the drug may elect to initiate phase IV trials. This phase includes continued
evaluation of the treatment effectiveness and monitoring of side effects as well
as implementing studies to evaluate usefulness in different types of cancers.