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What is a clinical trial?
A clinical trial studies people in a systematic way in order
to answer a question. The purpose of a clinical trial is to
find a better way to detect, prevent, control, or cure a disease
or disorder. Some trials test the effects of treatments on
disease, some aim to prevent disease, others study the effects
of the disease itself (quality of life, costs, comfort levels).
All of these types of trials may be found at the DCRI.
The search for better treatment begins with basic research,
in laboratories or in animals. This type of research points
out methods likely to provide positive outcomes and, as much
as possible, shows how to use them safely and effectively.
This early research cannot predict exactly how a new treatment
will work in people. Thus the clinical trial is done, in which
investigators try to duplicate in people the promising results
from basic research.
Clinical trials are primarily designed to test the effects
of a new or existing treatment on an illness or disorder.
The treatment can be a drug, a biological agent, a medical
device, or a behavioral change, but it needs to have shown
some promise in treating or preventing the health problem
before it can be tested in a clinical trial.
Clinical trials are carefully and ethically designed to
protect patients from unnecessary side effects and to allow
truthful and precise collection and analysis of information
to find out more about a disease. In general, clinical trials
offer hope for the successful treatment of a disease or illness
for future patients.
Why are clinical trials important?
Advances in medicine and science result from new ideas or
approaches developed through research. However, any new treatment
can carry risks as well as benefits. Clinical trials help
identify how safe and effective a treatment is for its intended
use. In the U.S., new drugs or devices must be shown to be
safe and effective in clinical trials of a certain number
of patients before the Food and
Drug Administration (FDA) can approve them for use. Until
then, they are considered investigational.
For existing treatments, clinical trials can find out which
might be the best for certain types of patients, which might
be the most cost-effective, or which might be easier to give.
Trials also can help confirm or refute common medical beliefs.
For example, aspirin's protective effects against heart attack
have been proven time and again. On the other hand, although
"everybody knows" that a diet high in fiber can
prevent colon and rectal cancer, a recent study has shown
that this conventional wisdom may be wrong.1
Why might I want to participate
in a clinical trial?
There are many reasons that people participate in clinical
trials:
- To contribute to research that could help others in the
future
- To receive effective treatment for a disease
- To achieve personal goals (stop smoking, for example)
- To seek relief or to feel better
- To obtain medical care
- To have access to treatments that may not be available
otherwise
How are clinical trials conducted?
Each trial is conducted under a protocol, a guide that spells
out what is to be done, how it is to be done, and why. Protocols
incorporate ways to answer research questions and to safeguard
the medical and mental health of patients. Some trials test
just one treatment in a group of patients. More typically,
a trial will include two or more groups who are as similar
as possible, each of which receives a different treatment
option: the treatment of interest, a standard treatment for
the disease (an active control), an inactive substance (a
placebo control), or no treatment at all. All of the groups
are then monitored in exactly the same way.
Several things (besides the treatment) can influence (or bias)
the results of the study. For example, if the groups being
studied are very dissimilar to begin with, any differences
between them at the end of the study may simply be an extension
of these baseline imbalances. If the groups are as similar
as possible to each other before treatment, it is more likely
that the treatment alone was responsible for any later differences
(good or bad) between groups. Another way to reduce the chance
of a physician or patient biasing the study results is randomization.
If a patient agrees to be randomized, he or she is assigned
by chance to either a treatment or a control group. The researchers
do not know which is better; both could be of equal benefit.
If the patients are unaware of the treatment they are given,
the study is said to be single-blinded. If the researchers
also are unaware of which treatment they are giving, then
the study is double-blinded.
If a study treatment is obviously not helping the patient,
the doctor can decide to remove the patient from the study.
The patient also can decide to withdraw and receive any other
available standard care. There are regular reviews of the
data from a trial, and the information is shared. If there
is clear evidence that one of the treatments is harmful or
ineffective, or if one treatment is substantially better than
another, the study is stopped earlier than planned. All patients
in the study are then treated according to the new information,
if they and their doctors so choose. The results of the study
often are published in medical journals such as the New
England Journal of Medicine or elsewhere.
Throughout a trial, the patient's personal doctor is kept
informed about the patient's progress. Patients are encouraged
to maintain contact with their referring doctors.
Why are trials divided into
phases?
Trials in each phase are designed to reveal certain information.
Patients may be eligible for studies in different phases depending
on their general condition and type of disease. More patients
take part in the later-phase studies than in earlier ones.
In a Phase I study, a new treatment is given to relatively
few people (20 to 100 healthy volunteers, typically). The
researchers must find the best way to give a new treatment
and how much of it can be given safely. They watch carefully
for any harmful side effects. The treatment has been tested
in laboratory and animal studies, but no one knows how people
will react. Phase I studies may involve significant risks
for this reason.
Phase II studies determine the treatment's effects on the
disease or disorder. This phase of testing usually involves
a few hundred patients, mostly those who have the disease
or disorder of interest. These are usually randomized, controlled
studies, so that the treatment's safety and effectiveness
(efficacy) can be measured more accurately. This stage of
drug development can last for up to 2 years.
Each new phase of study builds on information from previous
phases. If a treatment is shown to be effective in treating
the disease in Phase II, it moves on to Phase III testing.
Here it is compared with a placebo or with standard treatment(s),
to see which is more effective, or (in some cases) to see
whether it is at least as good as an existing treatment (equivalent).
These studies can go on for many years and can involve thousands
of people with the disease or disorder. After Phase III trials,
the drug or device company can request approval from the FDA
to sell the drug in the U.S. as a treatment for the particular
disease.
In Phase IV studies, the treatment has been approved for
a given use by the FDA, but certain aspects of the treatment
are examined in particular situations. For example, a new
drug may be tested in combination with other drugs, or in
other patient groups (children, for example). Phase IV trials
allow drug and device companies to identify side effects that
may not appear until very large numbers of patients have received
the treatment. Phase IV studies also are done to support other
uses for the drug or device, for example, treatment of another
disease.
References:
1. Fuchs CS, Giovannucci EL, Colditz GA, et al. Dietary
fiber and the risk of colorectal cancer and adenoma in women.
N Engl J Med 1999;340:169-76. |
