Clinical Trials: Questions and Answers 

Key Points 

• Clinical trials are research studies that test how well new medical approaches 

work in people (see Question 1). 

• Every clinical trial has a protocol, which describes what will be done in the 

study, how it will be conducted, and why each part of the study is necessary 

(see Question 4). 

• Informed consent is a process by which people learn the important facts about 

a clinical trial to help them decide whether to participate (see Question 6). 

• Payment of patient care costs in clinical trials varies by health insurance plan 

and by study (see Question 11). 

1. What are clinical trials, and why are they important?

Clinical trials are research studies that test how well new medical approaches work in 

people. Each study answers scientific questions and tries to find better ways to prevent, 

screen for, diagnose, or treat a disease. People who take part in cancer clinical trials have 

an opportunity to contribute to knowledge of, and progress against, cancer. They also 

receive up-to-date care from experts. 

2. What are the types of clinical trials?

There are several types of clinical trials: 

• Prevention trials test new approaches, such as medications, vitamins, or other 

supplements, that doctors believe may lower the risk of developing a certain type of 

cancer. Most prevention trials are conducted with healthy people who have not had 

cancer. Some trials are conducted with people who have had cancer and want to 

prevent recurrence (return of cancer), or reduce the chance of developing a new type 

of cancer. 

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• Screening trials study ways to detect cancer earlier. They are often conducted to 

determine whether finding cancer before it causes symptoms decreases the chance of 

dying from the disease. These trials involve people who do not have any symptoms 

of cancer. 

• Diagnostic trials study tests or procedures that could be used to identify cancer more 

accurately. Diagnostic trials usually include people who have signs or symptoms of 

cancer. 

• Treatment trials are conducted with people who have cancer. They are designed to 

answer specific questions about, and evaluate the effectiveness of, a new treatment or 

a new way of using a standard treatment. These trials test many types of treatments, 

such as new drugs, vaccines, new approaches to surgery or radiation therapy, or new 

combinations of treatments. 

• Quality-of-life (also called supportive care) trials explore ways to improve the 

comfort and quality of life of cancer patients and cancer survivors. These trials may 

study ways to help people who are experiencing nausea, vomiting, sleep disorders, 

depression, or other effects from cancer or its treatment.

• Genetics studies are sometimes part of another cancer clinical trial. The genetics 

component of the trial may focus on how genetic makeup can affect detection, 

diagnosis, or response to cancer treatment.

Population- and family-based genetic research studies differ from traditional cancer 

clinical trials. In these studies, researchers look at tissue or blood samples, generally 

from families or large groups of people, to find genetic changes that are associated 

with cancer. People who participate in genetics studies may or may not have cancer, 

depending on the study. The goal of these studies is to help understand the role of 

genes in the development of cancer.

3. Who sponsors clinical trials?

Government agencies, such as the National Cancer Institute (NCI) and other parts of the 

National Institutes of Health (NIH), the Department of Defense, and the Department of 

Veterans Affairs, sponsor and conduct clinical trials. In addition, organizations or 

individuals, such as physicians, medical institutions, foundations, volunteer groups, and 

pharmaceutical companies, also sponsor clinical trials. 

NCI sponsors a large number of clinical trials and has a number of programs designed to 

make clinical trials widely available in the United States. These programs include the 

following: 
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• The Cancer Centers Program provides support to research-oriented institutions, 

including those that have been designated as NCI Comprehensive or Clinical Cancer 

Centers for their scientific excellence. More information is available in the National 

Cancer Institute-Designated Cancer Centers Database, which is available at 

http://www.cancer.gov/cancertopics/factsheet/NCI/cancer-centers on the Internet. 

• The Specialized Programs of Research Excellence (SPOREs) bring together 

scientists and researchers to design and implement research programs that can 

improve prevention, detection, diagnosis, and treatment of specific types of cancer. 

More information about SPOREs is available at http://spores.nci.nih.gov/index.html 

on the Internet. 

• The Clinical Trials Cooperative Group Program brings researchers, cancer 

centers, and doctors together into cooperative groups. These groups work with the 

NCI to identify important questions in cancer research, and design and conduct 

multisite clinical trials to answer these questions. Cooperative groups are located 

throughout the United States and in Canada and Europe. For more information, refer 

to the fact sheet NCI’s Clinical Trials Cooperative Group Program at 

http://www.cancer.gov/cancertopics/factsheet/NCI/clinical-trials-cooperative-group 

on the Internet. 

• The Cancer Trials Support Unit (CTSU) makes NCI-sponsored phase III treatment 

trials available to doctors and patients in the United States and Canada. Doctors who 

are not affiliated with an NCI-sponsored Clinical Trials Cooperative Group (see 

above) must complete an application process, which includes credential verification 

and site preparedness assessment, to become members of the CTSU’s National 

Network of Investigators. CTSU members can enroll patients in clinical trials 

through the program’s Web site, which is located at http://www.ctsu.org on the 

Internet. General information about the CTSU is also available on the program’s 

Web site, or by calling 1–888–823–5923. 

• The Community Clinical Oncology Program (CCOP) makes clinical trials 

available in a large number of communities across the United States. Local hospitals 

throughout the country affiliate with a cancer center or a cooperative group. This 

affiliation allows doctors to offer people participation in clinical trials more easily, so 

they do not have to travel long distances or leave their usual caregivers. The 

Minority-Based Community Clinical Oncology Program focuses on encouraging 

minority populations to participate in clinical trials. More information about the 

CCOP can be found in the NCI fact sheet Community Clinical Oncology Program: 

Questions and Answers, which is available at 

http://www.cancer.gov/cancertopics/factsheet/NCI/CCOP on the Internet. 

• The National Institutes of Health Clinical Center, a research hospital located in 

Bethesda, Maryland, is part of the NIH. Trials at the Clinical Center are conducted 

by the components of the NIH, including the NCI. The NCI fact sheet Cancer 
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Clinical Trials at the National Institutes of Health Clinical Center: Questions and 

Answers has more information about the Clinical Center. This fact sheet is available 

at http://www.cancer.gov/cancertopics/factsheet/NCI/clinical-center on the Internet. 

4. How are participants protected?

Research with people is conducted according to strict scientific and ethical principles. 

Every clinical trial has a protocol, or action plan, which acts like a “recipe” for 

conducting the trial. The plan describes what will be done in the study, how it will be 

conducted, and why each part of the study is necessary. The same protocol is used by 

every doctor or research center taking part in the trial. 

All clinical trials that are federally funded or that evaluate a new drug or medical device 

subject to Food and Drug Administration regulation must be reviewed and approved by 

an Institutional Review Board (IRB). Many institutions require that all clinical trials, 

regardless of funding, be reviewed and approved by a local IRB. The Board, which 

includes doctors, researchers, community leaders, and other members of the community, 

reviews the protocol to make sure the study is conducted fairly and participants are not 

likely to be harmed. The IRB also decides how often to review the trial once it has 

begun. Based on this information, the IRB decides whether the clinical trial should 

continue as initially planned and, if not, what changes should be made. An IRB can stop 

a clinical trial if the researcher is not following the protocol or if the trial appears to be 

causing unexpected harm to the participants. An IRB can also stop a clinical trial if there 

is clear evidence that the new intervention is effective, in order to make it widely 

available. 

NIH-supported clinical trials require data and safety monitoring. Some clinical trials, 

especially phase III clinical trials, use a Data and Safety Monitoring Board (DSMB). A 

DSMB is an independent committee made up of statisticians, physicians, and patient 

advocates. The DSMB ensures that the risks of participation are as small as possible, 

makes sure the data are complete, and stops a trial if safety concerns arise or when the 

trial’s objectives have been met. 

5. What are eligibility criteria, and why are they important?

Each study’s protocol has guidelines for who can or cannot participate in the study. 

These guidelines, called eligibility criteria, describe characteristics that must be shared by 

all participants. The criteria differ from study to study. They may include age, gender, 

medical history, and current health status. Eligibility criteria for treatment studies often 

require that patients have a particular type and stage of cancer. 

Enrolling participants with similar characteristics helps to ensure that the results of the 

trial will be due to what is under study and not other factors. In this way, eligibility 

criteria help researchers achieve accurate and meaningful results. These criteria also 

minimize the risk of a person’s condition becoming worse by participating in the study. 
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6. What is informed consent?

Informed consent is a process by which people learn the important facts about a clinical 

trial to help them decide whether to participate. This information includes details about 

what is involved, such as the purpose of the study, the tests and other procedures used in 

the study, and the possible risks and benefits. In addition to talking with the doctor or 

nurse, people receive a written consent form explaining the study. People who agree to 

take part in the study are asked to sign the informed consent form. However, signing the 

form does not mean people must stay in the study. People can leave the study at any 

time—either before the study starts or at any time during the study or the follow-up 

period. 

The informed consent process continues throughout the study. If new benefits, risks, or 

side effects are discovered during the study, the researchers must inform the participants. 

They may be asked to sign new consent forms if they want to stay in the study. 

7. Where do clinical trials take place?

Clinical trials take place in doctors’ offices, cancer centers, other medical centers, 

community hospitals and clinics, and veterans’ and military hospitals in cities and towns 

across the United States and in other countries. Clinical trials may include participants at 

one or two highly specialized centers, or they may involve hundreds of locations at the 

same time. 

8. How are clinical trials conducted?

Clinical trials are usually conducted in a series of steps, called phases. Treatment clinical 

trials listed in PDQ®, the NCI’s comprehensive cancer information database, are always 

assigned a phase. However, screening, prevention, diagnostic, and quality-of-life studies 

do not always have a phase. Genetics clinical trials generally do not have a phase. 

• Phase I trials are the first step in testing a new approach in people. In these studies, 

researchers evaluate what dose is safe, how a new agent should be given (by mouth, 

injected into a vein, or injected into the muscle), and how often. Researchers watch 

closely for any harmful side effects. Phase I trials usually enroll a small number of 

patients and take place at only a few locations. The dose of the new therapy or 

technique is increased a little at a time. The highest dose with an acceptable level of 

side effects is determined to be appropriate for further testing. 

• Phase II trials study the safety and effectiveness of an agent or intervention, and 

evaluate how it affects the human body. Phase II studies usually focus on a particular 

type of cancer, and include fewer than 100 patients. 
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• Phase III trials compare a new agent or intervention (or new use of a standard one) 

with the current standard therapy. Participants are randomly assigned to the standard 

group or the new group, usually by computer. This method, called randomization, 

helps to avoid bias and ensures that human choices or other factors do not affect the 

study’s results. In most cases, studies move into phase III testing only after they have 

shown promise in phases I and II. Phase III trials often include large numbers of 

people across the country. 

• Phase IV trials are conducted to further evaluate the long-term safety and 

effectiveness of a treatment. They usually take place after the treatment has been 

approved for standard use. Several hundred to several thousand people may take part 

in a phase IV study. These studies are less common than phase I, II, or III trials. 

People who participate in a clinical trial work with a research team. Team members may 

include doctors, nurses, social workers, dietitians, and other health professionals. The 

health care team provides care, monitors participants’ health, and offers specific 

instructions about the study. So that the trial results are as reliable as possible, it is 

important for participants to follow the research team’s instructions. The instructions 

may include keeping logs or answering questionnaires. The research team may continue 

to contact participants after the trial ends. 

9. What are some of the benefits of taking part in a clinical trial? 

The benefits of participating in a clinical trial include the following: 

• Participants have access to promising new approaches that are often not available 

outside the clinical trial setting. 

• The approach being studied may be more effective than the standard approach. 

• Participants receive regular and careful medical attention from a research team that 

includes doctors and other health professionals. 

• Participants may be the first to benefit from the new method under study. 

• Results from the study may help others in the future. 

10. What are some of the possible risks associated with taking part in a clinical trial? 

The possible risks of participating in a clinical trial include the following: 

• New drugs or procedures under study are not always better than the standard care to 

which they are being compared. 

• New treatments may have side effects or risks that doctors do not expect or that are 

worse than those resulting from standard care. 

• Participants in randomized trials will not be able to choose the approach they receive. 
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• Health insurance and managed care providers may not cover all patient care costs in a 

study. 

• Participants may be required to make more visits to the doctor than they would if they 

were not in the clinical trial. 

11. Who pays for the patient care costs associated with a clinical trial?

Health insurance and managed care providers often do not cover the patient care costs 

associated with a clinical trial. What they cover varies by health plan and by study. 

Some health plans do not cover clinical trials if they consider the approach being studied 

“experimental” or “investigational.” However, if enough data show that the approach is 

safe and effective, a health plan may consider the approach “established” and cover some 

or all of the costs. Participants may have difficulty obtaining coverage for costs 

associated with prevention and screening clinical trials; health plans are currently less 

likely to have review processes in place for these studies. It may, therefore, be more 

difficult to get coverage for the costs associated with them. In many cases, it helps to 

have someone from the research team talk about coverage with representatives of the 

health plan. 

Health plans may specify other criteria a trial must meet to be covered. The trial might 

have to be sponsored by a specified organization, be judged “medically necessary” by the 

health plan, not be significantly more expensive than treatments the health plan considers 

standard, or focus on types of cancer for which no standard treatments are available. In 

addition, the facility and medical staff might have to meet the plan’s qualifications for 

conducting certain procedures, such as bone marrow transplants. More information about 

insurance coverage can be found on the NCI’s Clinical Trials and Insurance Coverage: 

A Resource Guide Web page at http://www.cancer.gov/clinicaltrials/learning/insurancecoverage on the Internet. 

Many states have passed legislation or developed policies requiring health plans to cover 

the costs of certain clinical trials. For more information, visit the NCI’s Web site at 

http://www.cancer.gov/clinicaltrials/developments/laws-about-clinical-trial-costs on the 

Internet. 

Federal programs that help pay the costs of care in a clinical trial include those listed 

below: 

• Medicare reimburses patient care costs for its beneficiaries who participate in clinical 

trials designed to diagnose or treat cancer. Information about Medicare coverage of 

clinical trials is available at http://www.medicare.gov on the Internet, or by calling 

Medicare’s toll-free number for beneficiaries at 1–800–633–4227 

(1–800–MEDICARE). The toll-free number for the hearing impaired is 

1–877–486–2048. Also, the NCI fact sheet More Choices in Cancer Care: 

Information for Beneficiaries on Medicare Coverage of Cancer Clinical Trials is 
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available at http://www.cancer.gov/cancertopics/factsheet/support/medicare on the 

Internet. 

• Beneficiaries of TRICARE, the Department of Defense’s health program, can be 

reimbursed for the medical costs of participation in NCI-sponsored phase II and 

phase III cancer prevention (including screening and early detection) and treatment 

trials. Additional information is available in the NCI fact sheet TRICARE 

Beneficiaries Can Enter Clinical Trials for Cancer Prevention and Treatment 

Through a Department of Defense and National Cancer Institute Agreement. This 

fact sheet can be found at 

http://www.cancer.gov/cancertopics/factsheet/NCI/TRICARE on the Internet. 

• The Department of Veterans Affairs (VA) allows eligible veterans to participate in 

NCI-sponsored prevention, diagnosis, and treatment studies nationwide. All phases 

and types of NCI-sponsored trials are included. The NCI fact sheet The NCI/VA 

Agreement on Clinical Trials: Questions and Answers has more information. It is 

available at http://www.cancer.gov/cancertopics/factsheet/NCI/VA-clinical-trials on 

the Internet. 

12. What are some questions people might ask their health care provider before 

entering a clinical trial? 

It is important for people to ask questions before deciding to enter a clinical trial. 

Questions people might want to ask their doctor or nurse include the following: 

 

The Study

• What is the purpose of the study? 

• Why do the researchers think the approach being tested may be effective? Has it 

been tested before? 

• Who is sponsoring the study? 

• Who has reviewed and approved the study? 

• What are the medical credentials and experience of the researchers and other study 

personnel? 

• How are the study results and safety of participants being monitored? 

• How long will the study last? 

• How will the results be shared? 

Possible Risks and Benefits

• What are the possible short-term benefits? 

• What are the possible long-term benefits? 

• What are the short-term risks, such as side effects? 

• What are the possible long-term risks? 

• What other treatment options are available? 
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• How do the possible risks and benefits of the trial compare with those of other 

options? 

Participation and Care

• What kinds of treatment, medical tests, or procedures will the participants have 

during the study? How often will they receive the treatments, tests, or procedures? 

• Will treatments, tests, or procedures be painful? If so, how can the pain be 

controlled? 

• How do the tests in the study compare with what people might receive outside the 

study? 

• Will participants be able to take their regular medications while in the clinical trial? 

• Where will the participants receive their medical care? Will they be in a hospital? If 

so, for how long? 

• Who will be in charge of the participants’ care? Will they be able to see their own 

doctors? 

• How long will participants need to stay in the study? Will there be follow-up visits 

after the study? 

Personal Issues

• How could being in the study affect the participants’ daily lives? 

• What support is available for participants and their families? 

• Can potential participants talk with people already enrolled in the study? 

Cost Issues

• Will participants have to pay for any treatment, tests, or other charges? If so, what 

will the approximate charges be? 

• What is health insurance likely to cover? 

• Who can help answer questions from the insurance company or health plan? 

13. What happens when a clinical trial is over?

After a clinical trial is completed, the researchers look carefully at the data collected 

during the trial before making decisions about the meaning of the findings and further 

testing. After a phase I or II trial, the researchers decide whether to move on to the next 

phase, or stop testing the agent or intervention because it was not safe or effective. When 

a phase III trial is completed, the researchers look at the data and decide whether the 

results have medical importance. 

The results of clinical trials are often published in peer-reviewed, scientific journals. 

Peer review is a process by which experts review the report before it is published to make 

sure the analysis and conclusions are sound. If the results are particularly important, they 

may be featured by the media and discussed at scientific meetings and by patient 

advocacy groups before they are published. Once a new approach has been proven safe 
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and effective in a clinical trial, it may become standard practice. (Standard practice is a 

currently accepted and widely used approach.) 

The National Library of Medicine’s Web site offers links to resources for finding the 

results of clinical trials. It includes information about published and unpublished results. 

This resource can be found at http://www.nlm.nih.gov/services/ctresults.html on the 

Internet. 

14. Where can people find more information about clinical trials? 

In addition to the resources described in Question 3, people interested in taking part in a 

clinical trial should talk with their health care provider. Information about cancer clinical 

trials is also available from the NCI’s Cancer Information Service (CIS). Information 

specialists at the CIS use PDQ to identify and provide detailed information about specific 

ongoing clinical trials. PDQ includes all NCI-funded clinical trials and some studies 

conducted by independent investigators at hospitals and medical centers in the United 

States and Europe. 

People also have the option of searching for clinical trials on their own. The clinical 

trials page of the NCI’s Web site, located at http://www.cancer.gov/clinicaltrials/ on the 

Internet, provides information about clinical trials and links to PDQ. Another resource is 

the NIH’s ClinicalTrials.gov Web site. ClinicalTrials.gov lists clinical trials sponsored 

by the NIH, other Federal agencies, and the pharmaceutical industry for a wide range of 

diseases, including cancer and other conditions. This site can be found at 

http://clinicaltrials.gov on the Internet. 

# # # 

Related NCI materials and Web pages: 

• National Cancer Institute Fact Sheet 1.3, Community Clinical Oncology Program: 

Questions and Answers

(http://www.cancer.gov/cancertopics/factsheet/NCI/CCOP) 

• National Cancer Institute Fact Sheet 1.4, NCI’s Clinical Trials Cooperative Group 

Program

(http://www.cancer.gov/cancertopics/factsheet/NCI/clinical-trials-cooperative-group) 

• National Cancer Institute Fact Sheet 1.13, TRICARE Beneficiaries Can Enter Clinical 

Trials for Cancer Prevention and Treatment Through a Department of Defense and 

National Cancer Institute Agreement

(http://www.cancer.gov/cancertopics/factsheet/NCI/TRICARE) 

• National Cancer Institute Fact Sheet 1.17, The NCI/VA Agreement on Clinical Trials: 

Questions and Answers

(http://www.cancer.gov/cancertopics/factsheet/NCI/VA-clinical-trials) 
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• National Cancer Institute Fact Sheet 1.22, Cancer Clinical Trials at the National 

Institutes of Health Clinical Center: Questions and Answers

(http://www.cancer.gov/cancertopics/factsheet/NCI/clinical-center)

• National Cancer Institute Fact Sheet 8.14, More Choices in Cancer Care: 

Information for Beneficiaries on Medicare Coverage of Cancer Clinical Trials 

(http://www.cancer.gov/cancertopics/factsheet/support/medicare)

• National Cancer Institute-Designated Cancer Centers Database

(http://www.cancer.gov/cancertopics/factsheet/NCI/cancer-centers)

• Taking Part in Cancer Treatment Research Studies 

(http://www.cancer.gov/clinicaltrials/Taking-Part-in-Cancer-Treatment-ResearchStudies)

For more help, contact: 

NCI’s Cancer Information Service 

Telephone (toll-free): 1–800–4–CANCER (1–800–422–6237) 

TTY (toll-free): 1–800–332–8615

LiveHelp® online chat: https://cissecure.nci.nih.gov/livehelp/welcome.asp

 

This fact sheet was reviewed on 5/19/06