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Home Clinical Trial Participation Types of Clinical Trials
Types of Clinical Trials PDF Print E-mail

Types of Clinical Trials

Purpose Number of people who take part
Phase I

To find a safe dose
To decide how the new treatment should be given
To see how the new treatment affects the human body

15-30 people
Phase II

To determine if the new treatment has an effect on a certain cancer
To see how the new treatment affects the human body

Less than 100 people
Phase III

To compare the new treatment (or new use of a treatment) with the current standard treatment

From 100 to thousands of people

Phase IV

To further assess the long-term safety and effectiveness of a new treatment

Several hundred to several thousand people

Most clinical trials have to go through different types of review that are designed to protect all people who take part. These reviews are conducted by scientific review panels, Institutional Review Boards (IRBs), and Data and Safety Monitoring Boards (DSMBs).

Scientific Review Panels

This panel is made up of experts who review a clinical trial protocol before it starts accepting patients to make sure it is based on sound science. All clinical trials that are funded by the Government must go through this review. Many other clinical trial sponsors, such as drug companies, also seek expert advice on the scientific merit of their trial protocols.

Institutional Review Boards

This board also reviews a clinical trial protocol before it starts accepting patients. The board members make sure the risks involved in the trial are reasonable when compared to the possible benefits. They also closely watch the ongoing progress of the trial from beginning to end.

Federal rules require that each IRB be made up of at least 5 people. One member must be from outside the institution running the trial. IRBs are usually made up of a mix of medical specialists and members of the community. Many include members from diverse careers and backgrounds. In most cases IRBs are located where the trial is to take place. Many institutions that carry out clinical trials have their own IRBs.

Data and Safety Monitoring Boards (DSMBs)

For phase III trials, DSMBs monitor the trial to help ensure your safety. They may also be appropriate and necessary for certain phase I and II clinical trials. A DSMB is an independent committee made up of statisticians, physicians, and other experts.

The Board must:

  • Ensure that any risks that come from being in the study are reduced as much as possible
  • Ensure that the data are sound
  • Stop a trial if safety concerns come up or as soon as its objectives have been met

Clinical Trials Follow Strict Guidelines

The guidelines that clinical trials follow clearly state who will be able to join the study and the treatment plan. Every trial has a person in charge, usually a doctor, who is called the principal investigator. The principal investigator prepares a plan for the study, called a protocol, which is like a recipe for conducting a clinical trial. The protocol explains what the trial will do, how the study will be carried out, and why each part of the study is necessary.

It includes information on:

  • The reason for doing the study
  • Who can join the study
  • How many people are needed for the study
  • Any drugs they will take, the dose, and how often
  • What medical tests they will have and how often
  • What information will be gathered about them

Who Can Join a Clinical Trial?

Based on the questions the research is trying to answer, each clinical trial protocol clearly states who can or cannot join the trial.

Common criteria for entering a trial:

  • Having a certain type or stage of cancer
  • Having received a certain kind of therapy in the past
  • Being in a certain age group

Criteria such as these help ensure that people in the trial are as alike as possible. This way doctors can be sure that the results are due to the treatment being studied and not other factors.

These criteria also help ensure:

  • Safety

Some people have health problems besides cancer that could be made worse by the treatments in a study. If you are interested in joining a trial, you will receive medical tests to be sure that you are not put at increased risk.

Accurate and meaningful study results

You may not be able to join some clinical trials if you already have had another kind of treatment for your cancer. Otherwise, doctors could not be sure whether your results were due to the treatment being studied or the earlier treatment.


Randomization is a process used in some clinical trials to prevent bias. Bias occurs when a trial's results are affected by human choices or other factors not related to the treatments being tested. Randomization helps ensure that unknown factors do not affect trial results.

In a randomized clinical trial, you will be assigned by chance to either a control group or an investigational group. Randomization is used in all phase III and some phase II trials. These trials are called randomized clinical trials. If you participate in such a trial, you will be assigned by chance to either an investigational group or a control group. Your assignment will be determined with a computer program or table of random numbers.

If you are assigned to the control group, you will get the most widely accepted treatment (standard treatment) for your cancer.

If you are assigned to the investigational group, you will get the new treatment being tested. Comparing these groups to each other often clearly shows which treatment is more effective or has fewer side effects. If you are thinking about joining a randomized clinical trial, you need to understand that you have an equal chance to be assigned to either one of the groups. The doctor does not choose the group for you.

Will I get a placebo?

A placebo is designed to look like the medicine being tested, but it is not active. Placebos are almost never used in cancer treatment trials. In some cases, a study may compare standard treatment plus a new treatment, to standard treatment plus a placebo. You will be told if the study uses a placebo.

Patient Protection

Federal rules help ensure that clinical trials are run in an ethical manner. Your rights and safety are protected through: Careful review and approval of the clinical trial protocol by two review panels. These panels include:

  • A scientific review panel
  • An institutional review board (IRB)

Ongoing monitoring provided during the trial by:

  • The IRB
  • Data and Safety Monitoring Boards (DSMBs) for phase III trials
  • Your research team

Informed Consent

Informed consent is a process through which you learn the purpose, risks, and benefits of a clinical trial before deciding whether to join. It is a critical part of ensuring patient safety in research. During the informed consent process you learn important information about a clinical trial. This information can help you decide whether to join. The research team, which is made up of doctors and nurses, first explains the trial to you.

The team explains the trial's:

  • Purpose
  • Procedures
  • Risks and benefits

They will also discuss your rights, including your right to:

  • Make a decision about participating
  • Leave the study at any time

If you decide to leave the study, your doctor will discuss other treatment options with you. Before agreeing to take part in a trial, you have the right to:

  • Learn about all your treatment options
  • Learn all that is involved in the trial - including all details about treatment, tests, and possible risks and benefits
  • Discuss the trial with the principal investigator and other members of the research team
  • Both hear and read the information in language you can understand

After discussing all aspects of the study with you, the team gives you an informed consent form to read. The form includes written details about the information that was discussed and also describes the privacy of your records. If you agree to take part in the study, you sign the form. Remember, even after you sign the consent form, you can leave the study at any time.

For more information please visit Clinical Trial Resources

Educational information provided by The National Cancer Institute (NCI) Internet site.
Last Updated on Tuesday, 24 February 2009 21:45
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