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Patients Participating in NCI Treatment Trials
Background
How many patients take part in NCI treatment trials?
How many patients enroll in NCI intramural trials?
How many patients enroll in NCI extramural trials?
How does the patient population enrolled in NCI clinical trials break down according to gender?
What percentages of adults and children with cancer enroll in NCI Cooperative Group trials?
Why is the proportion of cancer patients participating in clinical trials higher for children than
it is for adults?
What proportion of older cancer patients enrolls in NCI cancer treatment trials?
What proportions of participants in NCI treatment trials belong to racial or ethnic minority groups?
The significance and value of a clinical trial depend upon many factors, including the characteristics of the patients participating in the study. Depending on the purpose of the clinical trial, researchers enroll people who are alike in certain ways - for example, age, gender, and general health status. These characteristics are referred to as the trial's eligibility criteria, and they help to ensure that the results of the trial will be due to what is under study - for example, the drug being tested - and not to other factors.
Yet within the limits defined by the eligibility criteria, researchers also attempt to include as many types of people as possible in a trial so that the results will be as broadly applicable as possible. The more diverse the trial's population, the more useful the results could be to the general population. This is particularly true for relatively large phase III trials. Results of phase III trials should be as generally applicable as possible in order to benefit the maximum number of people.
From 2001 through 2003, an average of about 33,600 individuals enrolled in NCI treatment trials each year (internal data, unpublished). This figure includes patients who joined intramural clinical studies carried out at the NIH Clinical Center, located on the Bethesda campus, and patients who participated in extramural trials taking place at sites throughout the United States and in other parts of the world.
From January 2001 through December 2002, enrollment in NCI intramural clinical trials averaged almost 2,950 patients each year (internal data, unpublished).
Intramural clinical trials are planned, designed, and conducted by investigators in the NCI's
Center for Cancer Research, the larger of NCI's two intramural research divisions. Most intramural trials are relatively small phase I or phase II studies. Individuals participating in intramural clinical studies travel to the NIH campus from locations throughout the United States and around the world.
From January 2001 through December 2003, NCI programs supporting extramural clinical trials at the international, national, regional, and community levels enrolled about 30,660 patients annually (internal data, unpublished).
NCI's extramural clinical trial research enterprise includes the following components:
- The Cancer Therapy Evaluation Program (CTEP)
Part of NCI's Division of Cancer Treatment and Diagnosis, CTEP oversees all aspects of extramural clinical trials, including prioritization of clinical research initiatives, allocation of funds and other resources, clinical trial design, patient protections, and enforcement of standards governing data collection, monitoring, and reporting. One of CTEP's primary responsibilities involves promoting collaborations among basic scientists, academic researchers, practicing oncologists, and cancer experts both inside and outside the NIH.
- The Clinical Trials Cooperative Groups
The Cooperative Groups make up the largest collaborative clinical research
network administered by CTEP. From 2001 through 2003, they enrolled, on
average, more than 26,600 patients in extramural clinical trials each year
(internal data, unpublished). This figure represents about 86 percent of NCI's
total annual patient accrual.*
- The Community Clinical Oncology Program (CCOP)
The CCOP supports extramural trials through a network of community-based hospitals and medical practices that are affiliated with the Cooperative Groups. This program, administered by NCI's Division of Cancer Prevention (DCP), is responsible for approximately 30 percent of the accrual into extramural cancer treatment trials each year.*
NCI currently provides grants to 50 CCOP affiliates located in 30 states. Each affiliate is required to recruit at least 50 patients each year into treatment trials and another 50 individuals into control and prevention trials. To increase the participation of members of minority groups in clinical trials, DCP also provides grants to 13 minority-based CCOP affiliates. In addition, DCP provides grants to Cooperative Groups and NCI-designated Cancer Centers, which function as CCOP research bases, to design and conduct cancer prevention and control clinical trials through the CCOP networks. In 2004, CCOP affiliates collectively enrolled 6,000 patients into cancer treatment trials, and more than 7,900 participants into clinical studies involving cancer prevention and control (internal data, unpublished).
*Overlaps exist between the figures given for CCOP and those for Cooperative Group enrollment totals because these programs are interrelated.
From 2001 through 2003, approximately 63 percent of the participants in treatment trials overseen by CTEP were women and approximately 37 percent were men (internal data, unpublished).
Less than 2 percent of the adults diagnosed with cancer in the United States each year receive treatment through enrollment in an NCI Cooperative Group clinical trial.1, 2 This low rate of clinical trial participation lengthens the time required to meet patient accrual targets for trials and, therefore, lengthens the time required to complete clinical trials, slowing the pace of progress in improving cancer treatments.
In contrast to the low level of adult enrollment, 55 to 65 percent of children in the United States who are diagnosed with cancer by or before the age of 14 years enter an NCI-sponsored clinical trial. This percentage drops to about 10 percent for children diagnosed between the ages of 15 and 19 years.3
The following table* shows the percentages by age of all cancer patients who participated in CTEP-supported treatment trials from 2001 through 2003:
| Pediatric (under 21 years) | 11.0 % |
| Adult (21-64 years) | 60.0 % |
| Elderly (65 and older) | 29.0 % |
*Source: internal data, unpublished.
Experts suggest several reasons.
- Childhood cancers are rare diseases and, therefore, are often treated in large, specialized or academic treatment centers where many trials are in progress.
- The physicians who care for children with cancer are familiar with clinical trials and frequently talk to patients and families about trials.
- Most childhood cancers are leukemias and lymphomas, which have been the focus of intense research during recent decades, making an unusually large number of clinical trials available to patients.
An analysis of NCI Cooperative Group trial enrollment from 2001 through 2003 showed that 29 percent of trial participants were 65 years of age or older (internal data, unpublished). A similar analysis of NCI intramural clinical trials from 2001 through 2002 demonstrated that approximately 21 percent of the total number of participating patients belonged to this age group (internal data, unpublished).
Experts have suggested several possible explanations for the under-representation of older patients in cancer treatment trials.
-
Trials often have strict age requirements that prevent elderly patients from enrolling.4
- Older people often have other health problems (co-morbidities) or a history of earlier cancer that limits their ability to participate in trials.4-6
- Elderly patients may be taking drugs that increase the risk of dangerous drug-drug interactions with the medications being studied in a trial.4, 6
-
Older patients may be less aware of medical developments that reduce the toxicity of cancer treatments and are, therefore, less likely to seek out clinical trials.4
-
Physicians, patients, and family members may think that older patients are less likely to benefit from and less able to tolerate aggressive treatment.
- Finally, there may be a lack of financial, logistic, and social support for participation of older patients in trials.4-6
A study of participants in NCI Cooperative Group trials between 1991 and 1994 found that participation of African Americans and Hispanics was roughly proportional to the incidence of cancer (number of new cases per year) among these groups.7 Published data for the period ending in 2002 and unpublished data for the period from 2002 through 2003 from CTEP, which is summarized below, confirm this picture.
Ethnic Representation in CTEP Treatment Trials
|
Ethnicity
|
% of all participants* |
| Hispanic/Latino |
4
|
| Non-Hispanic/Latino White |
92
|
| Not reported or unknown |
4
|
*Source: internal data, unpublished.
Racial Representation in CTEP Treatment Trials
| Race |
% of all participants* |
| African American or Black |
7.46
|
| American Indian or Alaska Native |
0.36
|
| Asian |
2.06
|
| Native Hawaiian or other Pacific Islander |
0.25
|
| White (Hispanic and non-Hispanic) |
84.74
|
| More than one race |
0.05
|
| Not reported or unknown |
5.10
|
*Source: internal data, not published.
In recent years, the number of minority patients enrolled in cancer clinical trials has remained relatively stable, but the overall number of patients admitted to trials has increased, therefore decreasing the minority percentage.2
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