Cancer : Taking Part in Clinical Trials, Part 2

by National Cancer Institute

(Page 2 of 3)

How Do Researchers Design Prevention Trials?

A cancer prevention clinical trial that involves people results from a long and careful research process. As with other types of trials, each step, or phase, answers different questions about the sutdy agent which can be a medicine, vitamin, mineral, food supplement , or a combination of these.

Phase I trials are the first step in testing a prevention agent in people. Doctors try to find the best way to give the study agent (for example, by mouth), the best dose, and if there are any harmful side effects.

Phase II trials focus on learning whether the agent has a biologic effect in preventing cancer.

Phase III trials compare a promising new agent to the standard one or to no agent, using two groups of people.

Because less is known about possible risks and benefits in Phase I and II, these trials usually include only a small number of participants. In most cases, studies move into Phase III testing only after an agent shows promise in Phases I and II. Phase III trials may include hundreds of research centers around the country and hundreds or thousands of people.

Clinical trials follow strict guidelines for science and ethics. These guidelines deal with many areas, including the study's design and who can be on the study. Every trial has a chief investigator, who is usually a doctor. The investigator prepares a study action plan, called a protocol. This plan explains what the trial will do, how, and why. For example, it states:

• How many people will be in the study.
• Who is able to be in the study.
• What study agents people will take.
• What medical tests they will have and how often.
• What information will be gathered.

Every research center that takes part in the trial uses the same protocol. This ensures that information from all centers can be combined.

How Do Review Groups Protect Participants?

Clinical trials have several procedures to protect the safety of the people who join the study. Several groups have to approve the protocol for every study. Two of those groups are the sponsor of the study (for example, the National Cancer Institute) and the Institutional Review Board (IRB).

Every study center has an IRB, which includes doctors, other health care providers, consumers, and sometimes members of the clergy who do not have any personal interest in the results of the study which would bias them. They serve as neutral reviewers and ensure that the study is managed fairly and that no one is likely to be harmed who may decide to join. Each Phase III cancer prevention study also has a special group called a Data Safety and Monitoring Committee that looks at the test results and monitors the safety of the participants, and decides whether the study should go forward as originally planned.

What Happens in a Phase III Prevention Trial?

If you decide to join a Phase III cancer prevention trial, you'll work with a research team. Team members may include doctors, nurses, social workers, and other health care providers. They will give you clear instructions. You may be asked to take a medication. You also may be asked to keep a diary or answer questions about how you're feeling.

During the study, a research team will review your health carefully. (This means that you may have more tests and doctor visits than you would if you weren't in the study.) Team members also may check on you for a while after the trial ends (followup). To make the trial results as reliable as possible, it is important for you to follow the research team's instructions. That means having all doctor visits and tests, taking medicines on time, and filling out logs or answering questions. Careful review and followup help you and scientists find out quickly what agent is best for reducing cancer risk.

Who Can Participate?

Clinical trials try to enroll people who are alike in certain ways, depending on the study's purpose. Every protocol tells who can join that study and spells out the characteristics that people should have. These are called eligibility criteria. They may include age, gender, general health, and cancer risk factors.

Eligibility criteria are a key part of medical research. They help produce results we can trust. And after those results are known, the information can help doctors find out who will be helped by the approach being studied if it's shown to work. For example, a new drug may work for people with one type of risk factor but not for another, or it may work better for men than for women.

Eligibility criteria also help protect you. They help make sure that if you are likely to be harmed by something in the study design, you are not exposed to that risk.

How Are Participants Assigned to Groups?

Doctors use a process called randomization (chance) using a computer to assign you to either the intervention group or the control group in Phase III studies. This method ensures that certain factors and human choices don't affect study results, making them less reliable. When groups are compared with each other, it is clear whether the study agent works or has bad side effects. This also helps ensure that the findings really result from the study agent, and not from something else.

Most Phase III cancer prevention studies use a double-blind research design. This means that neither you nor the doctors know which people are taking the study agent or the control agent. Only the researchers at a central office know. Sometimes a doctor needs to find out if a participant has taken the study agent. A doctor can find this out, if needed, by talking with the central office staff.

No one knows whether it is better to be in the intervention or control group until the study is over and the results are ready. If that were known, there would be no need for the study. Either group may have good results or problems. The results help doctors decide whether to advise people to take the study agent for cancer prevention.

About the Author

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