You may have heard about clinical trials — studies of possible new treatments or medications — but wonder what exactly they are and if they might be right for you. Whether or not to participate in a clinical trial can be a complex decision. In order to make that decision, it may help you to learn more about what exactly clinical trials are and how new treatments are studied and approved for wider use.

Clinical trials are used in all specialties of medicine to test new forms of therapy. They're used to evaluate potential treatments that have had some effect against disease in the test tube, in animal experiments or in a limited number of patients. It's important to remember that approaches tested in clinical trials are potential treatments. They aren't established therapies or generally accepted treatments until they've been proved effective. Trials typically test new drugs, new approaches to surgery or radiation treatment, new combinations of existing treatments, or novel methods such as gene therapy.

All research should begin with a basic ethical question: "Do the potential benefits outweigh the potential harm?" Researchers design trials that allow them to learn as much as possible about a new treatment or medication in ways that minimize the risk of injury to participants.

The goal of clinical trials is to determine if a treatment works and is safe. Therapies that prove effective during trials may become the new standard of treatment for a condition. Comparing similar groups of people taking different treatments for the same type and stage of disease indicates that any benefits are due to the treatment rather than to chance or other factors.

Because research trials are primarily geared toward benefiting future patients with a particular illness, those who take part in the earliest studies of a treatment may not personally benefit from the treatment being tested. However, new therapies may sometimes be effective.

Medical research often takes place in five phases. Each phase has a different purpose. Treatments being tested must go through the testing phases in order.

Preclinical research refers to tests and trials that are performed on animals or in medical labs. Preclinical trials also help researchers identify potential treatments that are unsafe or ineffective. If an approach doesn't work in the laboratory, researchers will not test it in humans.

Phase I research is the first step in testing in humans. At this stage, researchers study:

• How much of the treatment to give
• How the human body reacts to the treatment
• How much can be given safely
• The best way to give the treatment
• Any harmful effects

Earlier studies have often only been done in animals, so the approach may pose some risks when first tried in humans. Researchers try to minimize these risks by starting with very small doses, and then increasing the dosage only if no or minimal side effects occur. Only a limited number of people who would not be helped by existing treatments are included in these trials. Between 20 and 80 volunteers typically participate in Phase I studies.

Phase II research focuses on determining whether a new approach works the way that it's intended. For example, does it shrink a tumor or improve the results of cancer-related blood tests? Researchers also monitor you for common short-term side effects that occur with the therapy. Some things aren't yet known about the treatment, so risks are still present. Several hundred people may participate in these studies.

Some clinical trials may compare a potential new treatment with a placebo — a pill or liquid that looks like the new treatment but has no active ingredients.

Phase III research usually begins only after a treatment shows promise in phases I and II. At this stage, you're often assigned randomly to receive either the experimental treatment or the standard treatment to avoid bias in the results.

Phase III trials provide more information about the safety of the experimental treatment and demonstrate whether the standard or the experimental treatment group has better survival rates and fewer side effects. These trials usually include several hundred to several thousand people. Large trials make it easier to estimate what would happen if the experimental treatment were available to everyone with the condition.

Phase IV research is done to follow what happens to people who use an experimental treatment after the Food and Drug Administration (FDA) has approved it. In these trials, the investigators record the side effects and results occurring in people who take a treatment or drug. Phase IV studies usually don't include a control group because the treatment has already been approved.

Phase IV trials aren't required for every treatment that's approved. In some cases, the FDA may require that a drug manufacturer perform the studies when the agency wants to be sure that there are no other side effects or that the known side effects aren't too serious. Sometimes drug companies launch Phase IV studies with the hope of collecting data that shows their drug is better than a competitor's product.

Clinical trials follow a scientific action plan (protocol). The protocol explains what will be done in the study and why. It outlines:

• Who may participate
• How many people will take part
• What the treatment plan entails
• The type and frequency of tests
• How the results will be measured
• The reasons why a study may be stopped
• The situations in which researchers may stop giving the treatment to participants

To ensure the safety of those in the study, the organization that sponsors the study, such as the medical center or clinic where the work will be done, must approve the protocol. In addition, an institutional review board (IRB) at each study site reviews the protocol. The IRB includes people from the community as well as health care professionals. It reviews all protocols to be sure that participants are treated humanely and ethically. The IRB also discusses such issues as whether the likely benefit of the treatment is worth its risk.

Informed consent is a critical part of ethical clinical research. If you're considering a trial, you must be given all available and useful information about a study before you decide whether to participate. The information should include details about the experimental treatments, tests that may be given, the possible risks and benefits of the tests and experimental treatments as well as information about any standard treatments available for your condition.

Before starting a trial, you must sign an informed consent form. This form explains what will happen during the trial and the known risks and benefits of participating in it. The form must explain this information in words you can understand. Researchers may not pressure you into signing up for a trial if you prefer not to get involved.

Signing the informed consent form means you agree to participate in the trial explained by the researcher and described on the consent form. If you later decide to leave the study, you may do so without any penalty.

In a very few cases, a trial participant may not sign an informed consent. If the participant is a young child, two steps are needed for informed consent. The parent must give informed permission, and the child must agree to enter the study. If the child is unable to agree — for example, if the child is an infant — a parent may consent instead.

After the first three phases have been completed, the company or researcher studying the treatment submits an application to the FDA asking permission to make the experimental treatment available to the public. The FDA puts together a panel of experts to review the research data and make a recommendation. The panel may:

• Recommend that the experimental treatment be approved for marketing as it was submitted
• Require the sponsor to make specific changes before marketing the experimental treatment
• Not approve the experimental treatment due to major problems

The FDA isn't required to do what the expert panel suggests, but it usually follows the panel's recommendation.

Learning about your disease and trying to decide on how to treat it can leave you feeling overwhelmed. Decide whether to participate in a clinical trial only after thinking about your preferences and talking with those close to you, with your doctor and with other health care professionals.