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Agency for Healthcare Research Quality

Cancer Clinical Trials, Recruiting Underrepresented Populations

Full Title: Knowledge and Access to Information on Recruitment of Underrepresented Populations to Cancer Clinical Trials

June 2005

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Structured Abstract

Context: Since the enactment of the National Institutes of Health (NIH) Revitalization Act in 1993, cancer researchers have made significant efforts to develop evidence regarding barriers to participation in clinical trials, especially for ethnic minority populations. While some advances have been made in defining these barriers, significant gaps remain in the available evidence in regard to efficacious and/or effective interventions to improve enrollment to cancer clinical trials. It is essential to address these gaps in the evidence, in order to fulfill the intent of the NIH Revitalization Act. Only a small proportion of cancer patients are enrolled in clinical trials, and recent evidence indicates that racial and ethnic minorities, adolescents, the elderly, rural populations and individuals of low socioeconomic status in general, are underrepresented in cancer clinical trials funded by the National Cancer Institute (NCI).

At the request and with the financial support of the NCI, the Agency for Healthcare Research and Quality (AHRQ) commissioned a systematic review of the existing evidence on the recruitment of underrepresented populations into cancer clinical trials, to be performed by the Johns Hopkins University Evidence-based Practice Center (EPC).

Objectives: We developed a conceptual framework to guide our analysis of barriers and promoters of participation of underrepresented populations in cancer clinical trials. Our approach takes account of the fact that in order to participate in a trial, an individual must be aware of the trial, have the opportunity to participate, and be willing to accept participation. The barriers and promoters span the continuum from awareness to acceptance, and they differ, depending on the population and whether recruitment is to a treatment trial or to a prevention trial. We performed a systematic review of evidence concerning the effectiveness of interventions designed to improve recruitment of these underrepresented populations into cancer therapeutic and prevention trials.

Our report focused on questions in the following areas:

  1. Methods used to study recruitment strategies.
  2. Measures of recruitment success.
  3. Comparison of two or more recruitment interventions for cancer treatment trials.
  4. Comparison of two or more recruitment interventions for cancer prevention trials.
  5. Barriers and promoters of recruitment.
  6. Physician attitudes and perceptions about recruitment.

Data Sources: Our comprehensive search plan included electronic and hand searching. In March 2004, we searched the following electronic databases: MEDLINE®, the Cochrane CENTRAL Register of Controlled Trials (Issue 1, 2003), the Cochrane Database of Methodology Reviews (CDMR), the Cumulative Index of Nursing and Allied Health Literature (CINAHL®), the Psychological Abstracts (PsycINFO), and The Campbell Collaboration's Social, Psychological, Educational, and Criminological Trials Register (C2-SPECTR). For hand searching, we identified 34 journals that we thought were most likely to contain relevant studies. We scanned the table of contents of the issues of these journals for relevant citations from January 2003 through July 2004.

Study Selection: Articles included in this evidence synthesis were English-language reports containing original data that addressed one of the specific research questions. We excluded articles that did not address underrepresented populations, did not address cancer treatment or prevention, or did not discuss recruitment to a controlled trial.

Data Extraction: Pairs of reviewers assessed the study quality and abstracted data for each eligible article. Data were entered into a relational database.

Data Synthesis: Overall, we identified 67 eligible articles that focused on the following areas: methods used to study recruitment strategies (n =13) measures of success (n =23), comparison of two or more recruitment interventions (n =5), barriers to and promoters of recruitment (n =45), and physician attitudes and perceptions regarding recruitment (n =10). These studies were heterogeneous in that they targeted community members, patients and physicians in a variety of contexts. Reports on methods to study recruitment interventions lacked consistency in reporting of target population characteristics such as age, gender, residence (urban or rural areas), socioeconomic status, and recruitment dates. All but two of the studies eligible for review regarding measures of success defined successful recruitment in a post-hoc fashion as actual participation of the targeted group; the studies rarely set specific recruitment goals a priori.

Only five studies compared two or more strategies to promote accrual to cancer clinical trials. Overall, the eligible studies identified 118 distinct barriers to accrual to cancer clinical trials, including 97 barriers to accrual to therapeutic trials, 18 barriers to accrual to prevention trials, and 32 barriers to accrual to both therapeutic and prevention trials. There were more reported barriers to opportunity (n = 80) than to awareness (n = 8) or acceptance (n = 40) of clinical trials. Of the 59 distinct promoters of enrollment, most (n = 28) were promoters of the opportunity to participate in a cancer trial.

There is a lack of information regarding efficacious recruitment strategies for all of the underrepresented racial and ethnic minority populations. Additionally, the available evidence suggests that the lack of availability of trials is a barrier to enrollment for the adolescent population. Moreover, study exclusion criteria such as age, comorbid conditions, functional status, and sometimes unwarranted provider concerns regarding drug toxicity, limit opportunities for the elderly to participate in cancer clinical trials. Transportation is an important barrier, among others, for rural populations.

The evidence suggests that provider attitudes and perceptions have a critical influence on enrollment results for underrepresented populations. Providers have declined to enroll patients because of their age, comorbid conditions, and mistrust of researchers; and for studies that targeted minority populations, mistrust of researchers and lack of provider awareness about trials were leading provider barriers that decreased patient enrollment in clinical trials.

The strengths of the available evidence are the identification of numerous barriers and promoters of accrual to cancer screening trials, and the consistency of these barriers across the available studies. The limitations in study design and reporting of some of the available studies represent an important weakness of this evidence. Many of the studies had important limitations in:

  • Representativeness.
  • Justification of study methods.
  • Reliability and validity of the data collection methods.
  • Potential for bias/confounding based on study design.
  • Failure to control for potential sources of bias in the data analysis.

Nevertheless, the evidence provides the basis for certain conclusions regarding future directions for research to improve enrollment of underrepresented populations in cancer clinical trials.

Conclusions: Clinical investigators need effective strategies to improve participation of underrepresented populations in cancer clinical trials. The available evidence is consistent regarding barriers that reduce awareness, the opportunity to participate, and acceptance of cancer clinical trials. However, the patterns of occurrence of these barriers differ among the underrepresented populations; and for this reason, research strategies must address the needs of each population with some specificity.

Future studies should build upon the existing evidence to further elucidate the nature of barriers and promoters of participation in cancer clinical trials. Research intervention strategies should be tailored to the specific context of an underrepresented population, to reduce barriers to awareness, opportunity, and acceptance of trial participation, and to demonstrate tangible results in terms of trial accrual. There are many barriers to enrollment in a cancer clinical trial, and piecemeal strategies will not suffice to ensure the participation of underrepresented populations. Research is needed on cost-effective strategies that bridge the cancer research center and the community in a manner that can be integrated into the context of the healthcare system and the clinical research team. Such research requires community involvement through all of its phases.

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Knowledge and Access to Information on Recruitment of Underrepresented Populations to Cancer Clinical Trials

Evidence-based Practice Center: Johns Hopkins University
Topic Nominators: National Cancer Institute, National Institute of Health (NIH)

Current as of June 2005

Internet Citation:

Knowledge and Access to Information on Recruitment of Underrepresented Populations to Cancer Clinical Trials, Structured Abstract. June 2005. Agency for Healthcare Research and Quality, Rockville, MD.


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