Clinical Trial Phases
Once a new treatment has been tested in the laboratory and
is proven safe for humans, clinical trials begin. Each trial
phase is designed to answer specific questions about the treatment.
I trials establish the safest dosage and best way to take
the drug, and they measure any side effects, or toxicities,
of the treatment. They involve a small number of volunteers,
usually less than 10014.
Since Phase I trials often destroy normal cells as well as
cancer cells, studies usually involve patients who have not
benefited from standard therapies15.
II trials look at the effectiveness of the treatment against
cancer and continue to examine safety and side effects. Often,
fewer than 100 patients participate and typically they are
patients who have tumors or cancer lesions that can be measured
before and after treatment16.
According to the National Cancer Institute, only one-third
of the drugs assessed in Phase II trials are found safe and
effective enough to go on to the next phase17.
III trials test the effectiveness of a new drug, combination
of drugs, or procedure. Unlike the first two phases, Phase
III trials require a large number of participants. In cancer
studies, patients are not given a placebo,
or inactive drug. In studies for cancer drugs, the patients
are randomly assigned to receive either the current gold
standard treatment, which is the best treatment available,
or the new treatment. The two treatments are compared for
effectiveness. As part of
informed consent, patients will receive continual updates
on the progress of the trial. If the experimental treatment
is not working, patients may choose to leave the trial and
take the standard treatment.
IV trials test a drug that is already marketed and available
for possible new uses. Phase IV studies also test new dosages
and ways of giving the drug.