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Cancer: Clinical Trials

What are clinical trials?

Clinical trials are research studies that help healthcare providers find ways to improve healthcare. Researchers do cancer clinical trials to look for better ways to treat cancer. Each study tries to answer scientific questions and to find better ways to prevent, diagnose, or treat cancer. You may be able to help with the research by enrolling in a clinical trial.

What are the different types of clinical trials?

There are several types of trials.

  • Treatment trials test:
    • new combinations of treatments
    • new cancer drugs
    • new approaches to surgery or radiation therapy
    • new methods, such as gene therapy.
  • Prevention trials test new ways of lowering the risk of getting cancer, such as medicines, vitamins, minerals, or other supplements.
  • Screening trials test the best ways to find cancer, especially in its early stages.
  • Quality-of-life trials explore ways to improve comfort and quality of life for people who have cancer. These studies are important because many people survive cancer for years after their diagnosis. These studies are also called supportive care trials.

What are the phases of clinical trials of a new drug?

Most research that involves the testing of a new drug moves ahead in a series of steps called phases. There are usually 3 phases:

  • Phase I trials test:
    • different ways to take a new drug (for example, by mouth or injection)
    • different dosages
    • the side effects of the drug.

    A phase I trial usually enrolls just a small number of people.

  • Phase II trials continue to test the safety of a drug and start looking at how well the new drug works.
  • Phase III trials compare a new drug with the current standard treatment. Participants are usually randomly assigned to either the group receiving the standard treatment or the group receiving the new treatment. Phase III trials often enroll large numbers of people. They may be conducted at many doctors' offices, clinics, and cancer centers nationwide.

An important thing to know about cancer clinical trials is that they do not use placebos. Placebos are "blanks," that is, pills or injections that do not contain any medicine. Sometimes people worry that participating in a cancer clinical trial will mean that they will not be given any treatment. In cancer research new drugs and treatments are compared with known treatments, not with a lack of treatment.

What happens during a trial?

If you decide to take part in a trial, you will work with a research team. Team members may include doctors and other healthcare providers. They will give you specific instructions about the study, provide your care, and check your health carefully during the study.


Participating in a trial may mean that you have more tests and doctor visits than you would if you were not in the study. To make the trial results as reliable as possible, you must follow the research team's instructions. That means carefully following the schedule for all doctor visits and tests, taking medicines on time, and completing logs or answering questionnaires.

What are the potential risks and benefits of clinical trials?

Some of the possible benefits are:

  • You may get healthcare from leading doctors in the field of cancer research, including experts on your type of cancer.
  • You may be able to get new treatments before they are widely available.
  • Your overall health may be more closely watched.
  • You will have a chance to make a valuable contribution to cancer research.

Possible risks include:

  • New drugs and procedures may have side effects or risks unknown to the researchers.
  • New drugs and procedures may not help, or they may not work as well as other treatments.
  • Even if a new treatment has benefits, it may not work for you.

How are participants protected?

The US government has a system for protecting people who take part in these studies. Before a government-funded clinical trial can start, the trial plan must be approved. During the trial, review committees make sure that the plan is being followed and participants are being protected.


Regulations require researchers to tell you about a study's treatments, tests, and possible benefits and risks before you decide to join the trial. This process is called informed consent.

What happens when a clinical trial is over?

After a phase I or phase II trial is completed, the researchers look carefully at the data collected during the trial and decide whether to:

  • Move on to the next testing phase with the treatment, or
  • Stop testing the treatment because it is not safe or not effective.

When the analysis of a trial is complete, the researchers will share the results with the medical community and the public. In most cases, the results of trials are published in scientific or medical journals.

How do I know if I can be part of a clinical trial?

Each study has guidelines for who can take part, called eligibility criteria. Eligibility criteria for a treatment trial might be:

  • a particular type and stage of cancer
  • age
  • gender
  • previous treatments you have had.

To find out if you are eligible for a particular study, talk to your healthcare provider or the provider in charge of enrolling people in the study.

Should I take part in a clinical trial?

Only you can make the decision about whether or not to participate in a clinical trial. Before you make your decision:

  • Learn as much as you can about your disease and the trials that are available to you.
  • Talk about this information and how you feel about it with your healthcare provider, family members, and friends.

When you talk with your healthcare provider, some of the questions you may want to ask are:

  • What is the purpose of the trial?
  • What tests and treatments are involved?
  • How long will I be involved with the study?
  • What side effects can I expect?
  • How will the side effects be managed?
  • What costs will I be responsible for?
  • What happens if I want to stop being in the study?
  • Will my participation in the clinical trial decrease my chances of survival?

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Disclaimer: This content is reviewed periodically and is subject to change as new health information becomes available. The information provided is intended to be informative and educational and is not a replacement for professional medical evaluation, advice, diagnosis or treatment by a healthcare professional.


HIA File canc3515.htm Release 13/2010

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