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 here.
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.
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 two 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.
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.