About Clinical Trials

Approved by the Cancer.Net Editorial Board, 08/2019

A clinical trial is a research study that involves people. These studies help doctors find better ways to treat and prevent cancer and other diseases.

Why are clinical trials done?

Clinical trials are the main way that doctors find better treatments. There are clinical trials for cancer and other diseases. Clinical trials also help doctors learn how to prevent disease or treat symptoms and side effects.

In the United States, the Food and Drug Administration (FDA) says new drugs and other treatments must be tested in clinical trials. This must happen before the FDA approves the drug or treatment for everyone to use.

There are always many clinical trials going on. This is because doctors always need new information and ways of treating cancer. If you or a loved one has cancer, you might consider joining a clinical trial. You might do this to try a new drug or treatment. Or you might join one to help doctors develop better treatments for the future.

What are the different types of clinical trials?

There are 4 different types. The information below explains them.

Clinical trials for new treatments

Most clinical trials are this type. These clinical trials might study:

  • A new drug or combination of drugs

  • A new way of doing surgery or giving radiation therapy

  • A new way to give treatments

  • Behavioral changes, such as exercise and diet, that can help people live longer

Doctors call the treatment they use already the "standard of care." They want to learn if a new drug or treatment works as well or better. They also want to learn about side effects and make sure these are not too severe.

Clinical trials for side effects and symptoms

Doctors are always looking for ways to make people with cancer feel better. So they do clinical trials for side effects and symptoms. For example, some chemotherapy drugs can make you vomit (throw up). Doctors did clinical trials of drugs to prevent nausea and vomiting. Now, people getting chemotherapy do not usually get as sick as in the past. This is the result of clinical trials to develop anti-nausea drugs.

Clinical trials for long-term side effects

Today, doctors cure more than half of all cancers. But cancer treatment can cause side effects many years after you are cured. For example, some treatments can cause heart problems later in life. Doctors call these side effects "late effects." They do clinical trials to prevent and treat late effects in people with cancer.

Clinical trials to prevent and look for cancer

Doctors do clinical trials to find new ways to prevent cancer, reduce people's risk of cancer, or find it early. Early treatment is often more effective. Questions they study in these types of trials include:

  • How can we keep people from getting this type of cancer?

  • Is this cancer inherited, or passed on from parent to child?

  • Can we keep an inherited cancer from developing? Can we find it earlier or warn people they could get it?

  • Can you prevent or reduce the risk of this cancer by eating or avoiding certain foods? Taking or avoiding certain medicines?

  • Does it help to make life changes, such as getting more sleep or exercise?

How do clinical trials work?

Each clinical trial follows a specific set of rules. Doctors call these rules the “protocol.” Every trial has its own protocol, but it must always include:

  • Who can be in the clinical trial and who cannot

  • When you receive the clinical trial treatment, how often, and how much

  • When you have medical tests and procedures

  • How long the clinical trial lasts

  • How doctors will compare the different treatments in the clinical trial

How do doctors decide if I can be in a clinical trial?

Clinical trials involve volunteers. If you choose to join a clinical trial, the doctors will check whether that specific clinical trial is right for you. To decide who can join a specific clinical trial, they look for volunteers who have certain things in common, including:

  • Age

  • Cancer type or stage

  • Certain health problems or conditions, now or in the past

  • Your health now

  • Any treatments you already had

Doctors call these requirements the "eligibility criteria." For example, a clinical trial might be for people over 50. If you are younger than 50, that specific trial is not right for you. But you may be able to join a different one.

Doctors also decide if it is safe for you to join a clinical trial. They consider:

  • Any health problems or conditions, now or in the past

  • Your general health now

  • If the clinical trial treatment is safe for you

You should not feel bad if your doctor says you cannot join a specific clinical trial. The doctor and clinical trial staff want to keep you safe. They also need to make sure the clinical trial treatment is right for you.

How does the clinical trial staff keep me safe?

The doctor and other health care staff check your health regularly during the clinical trial. Clinical trial staff include nurses, researchers, and other health care professionals.

Before you start a clinical trial, the staff will answer any questions you have. They review all the clinical trial information with you. If you understand, and you then decide you want to join the clinical trial, they help you join.

During the clinical trial, the research team will check your health regularly. They will tell you about any tests and procedures you need.

The staff may check on you for several weeks, months, or longer after the clinical trial. They want to know if the treatment causes any problems. They might also want to know how long it works.

What should I do if I am in a clinical trial?

You should:

  • Follow instructions from the research team

  • Ask questions about anything you do not understand

  • Tell the research team if you have a new health problem. It might be a side effect of the clinical trial treatment.

  • Tell the research team if you are worried about anything

It is important to tell the research team about your health during the clinical trial and later. They want to know all the details of your health so they can keep you safe.

Will I know what treatment I get?

Maybe. In some clinical trials, the research team knows what treatment you get, but you do not. In other trials, no one knows, including the research team. And sometimes, everyone knows, including the patients. Talk with the research team ahead of time about the structure of the study you are interested in joining.

What are the phases of clinical trials?

"Phases" are the steps a clinical trial must go through. The main phases of a clinical trial are phase I, phase II, and phase III. Doctors gather different information about the treatment in each phase.

Clinical trial phases are different from cancer stages. Cancer stages tell you how much cancer there is and how far it has spread. Clinical trial phases describe different things doctors are studying about a new drug or treatment.

You do not have to go through each phase of a clinical trial. You can join or leave a trial at any phase.

Learn more about phases of clinical trials.

Can a clinical trial help my cancer?

It might. Clinical trials give hope to many people with cancer.

If you or a loved one has cancer, your doctor might ask if you want to be in a clinical trial. If you join, you receive the same level of care as with regular cancer treatment. Also, the clinical trial treatment may help you.

You should know that it can take a long time to get results of the full clinical trial. This is because the study may include hundreds of people, or even thousands. It can take a long time to study all the results.

You should also know that clinical trials need people of all ages. Right now, more children join clinical trials than adults. More than 60% of children with cancer join a clinical trial. Of these, 75% live a long time after cancer. Fewer than 5% of adults join a cancer clinical trial. About half of these adults live a long time after cancer.

Learn more with free videos

PRE-ACT, Preparatory Education About Clinical Trials

You can watch a free series of educational videos on Cancer.Net. The series is called Preparatory Education About Clinical Trials, or PRE-ACT.

For a personalized video series, answer questions about your own situation and create an account. You may also watch the whole series. With your account, you can start and stop watching any time.

Related Resources

Finding a Clinical Trial

Cancer.Net Video: What are Clinical Trials, with Richard Goldberg, MD

Cancer.Net Video: Types of Cancer Clinical Trials, with Louis Weiner, MD

More Information

Cancer Support Community: Frankly Speaking About Cancer Clinical Trials (PDF)

Center for Information and Study on Clinical Research Participation

ClinicalTrials.gov: Learn About Clinical Studies

ASCO Answers: Cancer Clinical TrialsDownload a free fact sheet on Cancer Clinical Trials (PDF).  This 1-page (front and back) fact sheet provides an introduction to cancer clinical trials, including a description what a clinical trial is, why clinical trials are important, patient safety, common concerns, words to know, and questions to ask the health care team and clinical trial staff. Order printed copies from the ASCO Store