About Cancer Clinical Trials

Approved by the Cancer.Net Editorial Board, 09/2023

A research study involving volunteers is called a clinical trial. This type of study helps doctors and researchers find better ways to care for people with cancer and other diseases. They can be used to study new and better ways to treat and prevent cancer, relieve side effects, and improve outcomes for people with cancer.

This article is about the basics of cancer clinical trials. Learn more about the phases of clinical trials and patient safety in clinical trials.

What are the different types of cancer clinical trials?

There are 4 different categories of clinical trials:

Clinical trials for new treatment. Most clinical trials are done to test new treatments. These clinical trials might study:

  • A new drug

  • A new combination of drugs

  • A new way of doing surgery or giving radiation therapy

  • A new way to give treatments

  • Changes, such as to nutrition and exercise, that can help people live longer

Doctors call the known treatment they use already the "standard of care." Clinical trials help them learn if a new drug or treatment works as well or better than the standard of care. Through this kind of clinical trial, they will also learn more about a new treatment's side effects.

Clinical trials for symptoms and side effects during treatment. Doctors also want to learn how to help people with cancer feel better. Cancer clinical trials are also done for side effects and symptoms.

For example, some chemotherapy drugs can cause nausea and vomiting. In recent years, clinical trials have found different ways to prevent and treat nausea and vomiting caused by chemotherapy. Now, people getting chemotherapy do not usually get as sick as they did in the past. This is the result of clinical trials to develop anti-nausea drugs.

Clinical trials for late effects. Today, many cancers are cured through treatment. But cancer treatments can cause side effects many years after you are cured, called long-term and late effects. For example, some treatments can cause heart problems later in life. Clinical trials can help researchers learn how to prevent and treat late effects for cancer survivors.

Clinical trials to prevent and look for cancer. Clinical trials are also done to find new ways to prevent cancer, reduce cancer risk, and find cancer earlier. This is important because early treatment often works better. These kinds of clinical trials look at:

  • How can this kind of cancer be prevented? Or can the risk of this cancer be lowered?

  • Is this cancer inherited? This means a genetic risk for this cancer can be passed from parent to child.

  • Is there a way to prevent inherited cancers from developing? How can people be aware of the risk?

  • Can the risk of cancer be reduced by eating or avoiding certain foods? By taking or avoiding certain medicines?

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

Learn more about understanding cancer research study design.

Why are clinical trials done?

Clinical trials are a way to make sure that treatments are safe and effective. In the United States, the U.S. Food and Drug Administration (FDA) says new drugs and other treatments must be tested in clinical trials. Every drug and treatment must go through several different clinical trials before it can be approved.

Clinical trials can tell doctors and researchers many different things about a treatment. For example:

  • Is the treatment safe?

  • Is the treatment effective?

  • Does the treatment work better than an existing treatment?

  • Does the treatment work for everyone with a specific illness? Or does it only work for some people?

  • What dose of the treatment works best?

  • Does the treatment cause side effects? If so, how severe are they?

There are always many cancer clinical trials going on. This is because doctors and researchers are always trying to find new and better ways to treat cancer and to care for people diagnosed with cancer. Clinical trials may be an option for treatment for anyone with cancer. Talk with your health care team about your treatment options. Learn more about how to find cancer clinical trials.

How can I find a cancer clinical trial?

First, talk with your cancer care doctor about whether or not treatment through a clinical trial is an option for you. They can help you find clinical trials that are open to you (see "How do doctors decide if I can be in a clinical trial?" below).

You can also see which clinical trials are searching for volunteers right now. There are many different online databases that can help you find this information. There are also programs that will match you with a clinical trial.

Learn more about how to find a cancer clinical trial.

What is a clinical trial protocol?

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

  • Who can be in the clinical trial and who cannot, called its "eligibility criteria"

  • When the study's participants receive the treatment, how often, and how much

  • When the participants will have certain medical tests and procedures

  • What questionnaires participants will be asked to complete to track how they are feeling and functioning

  • How long the clinical trial lasts

  • How doctors will compare the different treatments in studying the results of the clinical trial

What are clinical trial phases?

"Phases" are the steps a clinical trial must go through. There are 3 main phases of a clinical trial: 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. Staging a tumor 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. The phase only describes where the researchers are in the process of studying a new treatment or topic.

Learn more about the phases of clinical trials.

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

If you choose to join a clinical trial, the study's researchers will check if 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. This may include:

  • Cancer type, stage, or grade

  • Specific genetic changes, called mutations or alterations

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

  • Your health now

  • Any treatments you already had

  • Age

Together, a study's requirements on who can or cannot join are called the eligibility criteria. For example, some clinical trials focus on how treatments affect adults age 65 and older. If you are younger than 65, that study 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 will consider:

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

  • Your general health now

  • If the clinical trial treatment is safe for you

Learn more about eligibility criteria for cancer clinical trials.

What should I do if I enroll in a cancer clinical trial?

When you decide to join a cancer clinical trial, the study's researchers and staff will provide you with many details about that clinical trial. When you meet them about the clinical trial and throughout the clinical trial, make sure you:

  • Follow instructions from the research team

  • Ask questions about anything that is unclear

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

  • Tell the research team if you have any worries or concerns

It is important to let the research team know about any changes to your health during the clinical trial and later. This will help them keep you safe.

Clinical trial volunteers may decide to stop participating in the study at any time, for any reason.

How does the clinical trial staff keep me safe?

If you join a clinical trial, the doctor and other health care staff will 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 will review all the clinical trial information with you. If you decide to join the clinical trial, they will help you join, called enrollment.

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 even years. They want to know how you are feeling, how well the treatment works, how long it works, and if it causes any problems.

Learn more about patient safety during clinical trials.

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 clinical trials, no one knows, including the research team, until the study is complete and all data are analyzed. This can sometimes take years. 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.

Sometimes, placebos are used during cancer clinical trials. A placebo is a drug or treatment that is not active. It is sometimes called a "sugar pill." When they are used, placebos are usually combined with standard treatment in most cancer clinical trials. This means the participant will be receiving the standard of care for that type of cancer. When researchers use a placebo, they must:

  • Tell participants that they have a chance of getting a placebo

  • Tell them if they will receive an experimental treatment at some point in the clinical trial, if not right away

Learn more about how placebos are used in cancer clinical trials.

When should I consider joining a clinical trial?

You can join a clinical trial at any point during your cancer treatment. If you join one, you will receive the same level of care as with regular cancer treatment.

People join cancer clinical trials for many different reasons. For some, a clinical trial is the best treatment option available. Others are willing to face the added uncertainty of a clinical trial because standard treatments are not perfect and they are hoping for a better result. Others volunteer for clinical trials because they know that these studies are a way to contribute to progress in treating cancer.

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.

What happens if my cancer gets worse during a cancer clinical trial?

You can stop participating in a clinical trial at any time. This includes if your cancer gets worse while receiving treatment as part of a clinical trial. If you decide to leave the clinical trial, you will discuss with your cancer care team your treatment options. Learn more about patient safety during cancer clinical trials.

How will I pay for treatment during a cancer clinical trial?

If you are in the United States, you may have concerns about whether or not your cancer care is covered by health insurance if you join a clinical trial. Recent changes to the U.S. health care laws mean that most routine care costs from clinical trials are covered by most health insurance policies, including Medicaid. Other costs are covered by the study's researchers or sponsor. Before deciding to join a cancer clinical trial, talk with the researchers and your insurance company to confirm what costs are covered and who will cover them. Note that some trials require extra visits which can lead to travel costs and/or loss of work or childcare expenses.

Learn more about health insurance coverage of clinical trials.

What happens when a cancer clinical trial ends?

You may have many questions about what happens when a cancer clinical trial ends. For example, you may wonder if you can continue receiving the treatment or if there are additional clinical trials you can participate in. What happens next depends on the type of trial you are participating in and the results of the study. But you should always be informed about your options before the clinical trial begins.

It can take time for a drug that was studied in a clinical trial to be approved by the FDA and become available to the public. Because of this, it is important to know what your options are after the clinical trial has ended. Sometimes, the manufacturer of the treatment makes the treatment available to clinical trial volunteers when the study is over. Other times, the manufacturer can make the treatment available to purchase, though insurance may not cover this cost. In other cases, the drug or treatment tested during the clinical trial may not be available.

Sometimes, a clinical trial can end unexpectedly. This may happen because:

  • The results showed that the drug was so effective that the results need to be presented right away. It would be unfair to continue the clinical trial for the people in the control group receiving the current standard of care.

  • There are safety concerns.

  • Early results show that the treatment is not going to be effective.

Before you decide to participate in a clinical trial, ask what will happen if the trial has to end for any reason. Ask how the information will be shared with you.

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

Questions to Ask About Clinical Trials

How I Took Charge of My Cancer Care and Found a Clinical Trial that Was Right For Me

Deciding on a Cancer Clinical Trial? 4 Things to Ask

Reducing Health Care Disparities Through Cancer Clinical Trials

When Joining a Cancer Clinical Trial is Your Last Treatment Option

How Can I Get the Latest Cancer Drug?

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