A fundamental goal of cancer centers is to improve cancer care through the design and conduct of therapeutic clinical trials.1 Progress in prevention and control of cancer depends on research that identifies treatments that prevent or delay death caused by cancer or improve quality of life for patients living with cancer. Clinical trials, to whatever extent possible, should address disease across broad categories of age, sex, race, and ethnicity,2 both to ensure that targeting of interventions can be fine-tuned and generalizability of results.3 Clinical trial participation may be one way to assess diversity and equitable access to cutting-edge cancer care.4,5
Cancer centers are charged with ensuring equitable access to care among patients. Equitable access is inherently multidimensional, with patient/case characteristics, such as cancer type, stage, age, race, ethnicity, sex, socioeconomic class, education level, marital status, and comorbid conditions, affecting participation. Thus, depending on how the question is framed, equitable access can be defined across multiple patient or case subgroups. From the standpoint of NCI reporting, assessment of diversity in clinical trial participation has been accomplished primarily by comparing the proportions of racial and ethnic categories across1 the population from which a cancer center draws (an institution-defined catchment area),2 the cancer cases seen within the center,3 and the participants in therapeutic clinical trials.6 Two limitations of this approach are that the determination of catchment area from which a cancer center draws may be somewhat arbitrary and designated without regard to patient willingness to travel for care,1 and that percent participation is influenced by a host of factors outside the control of the institution, including health insurance coverage, referral patterns, cultural preferences, and competing providers.2,7–9
The Sidney Kimmel Comprehensive Cancer Center at Johns Hopkins (JH SKCCC) is situated in the city of Baltimore, where two thirds of the population consists of racial minorities (non-white). Cancer treatment services are provided by many other hospitals in Baltimore City.10 The JH SKCCC catchment area was defined through a data-based cluster assessment, using SaTScan, as a contiguous cluster of 58 counties centered on Baltimore City. The defined catchment area has remained stable.11
Catchment or health service areas are characterized by a balance of market share and proximity.12,13 Moreover, there is a distance over which patients are willing to travel for the service provided, irrespective of disease.14 We would expect this to be true for those participating in cancer clinical trials. The authors' previous research found that size of the catchment area for the JH SKCCC differs between whites and blacks (58 vs. 15 counties, respectively), a finding that might contribute to clinical trial enrollment disparities.11 The authors were also interested in how well JH SKCCC served Baltimore City as the immediate neighborhood, and therefore assessed 3 main geographic areas: Baltimore City, the remainder of the catchment area, and the non–catchment area as defined by county of residence. Using these geographic definitions, the authors hypothesized that overall, therapeutic and nontherapeutic clinical trial participation and clinical trial participation according to race also may vary by location. They assessed the clinical trial accrual to cancer case ratio (ACR) in this study to simultaneously evaluate racial and geographic disparities, including a race–geographic area interaction, at JH SKCCC. Independent effects and differences accounted for by sex, age, cancer site, and county poverty also were examined.
The authors have disclosed that they have no financial interests, arrangements, or affiliations with the manufacturers of any products discussed in this article or their competitors. This work was supported in part by the Maryland Cigarette Restitution Fund at the Johns Hopkins Sidney Kimmel Comprehensive Cancer Center.
The authors would like to thank Dr. Shu-Chih Su, who originated the catchment area definition and commented on drafts of the paper.
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