Twenty years after the National Institutes of Health (NIH) Revitalization Act established a mandate for more appropriate representation of minority groups in NIH-funded research, the degree of focus on minorities in US clinical trials sponsored by the National Cancer Institute (NCI) remains “woefully inadequate”, a new review has found.

The findings are particularly worrying given the growing share in the US population of ethnic and racial minorities who record the highest incidence of, and mortality rates for, cancer, point out Professor Moon Chen and colleagues from the UC Davis Comprehensive Cancer Center in Sacramento.

To assess the degree of minority inclusion in oncology trials, Chen and his team searched the registry for NCI-sponsored trials available during the month of January 2013. Results were published online in the journal Cancer.

They refined this search using terms for different minority groups (e.g., “black,” “African American,” “Hispanic”, “Latino”), then counted the number of clinical trials with a primary focus on a particular ethnic or minority population.  

Only around 150 out of some 10,000 trials, or less than 2% of the total, met these criteria, Chen et al found

PubMed review

The researchers also reviewed abstracts and articles accessed from January through to March 2013 on PubMed, the online database of published research findings, to identify articles that specifically examined minority accrual in clinical trials.

The search terms “NIH Revitalization Act of 1993”, “enhancing minority participation in cancer clinical trials,” “minority participation in cancer clinical trials,” and “increasing minority accrual in clinical trials” generated 42 citations, of which only five included reports explicitly discussing participation levels by race and ethnicity.  

The five key findings of the analysis by Chen’s team were:

  • The numbers and percentages of cancer clinical trials focusing primarily on racial/ethnic minority populations are “extremely” low.

“Cumulatively, it would appear that the percentage of NCI-sponsored clinical    trials in which racial/ethnic minorities represent the major emphasis … is  approximately 100 of 10,000 individuals or, at best, 1%,” the researchers state.                                                

  • The proportion of minority adults enrolled in cancer clinical trials is not adequate or representative of the US population with cancer.   

For example, cancer-incidence rates show that blacks experience the highest oncology burden (593.7 per 100,000), followed by whites (513 per 100,000),  Hispanics (395.2 per 100,000), Asians/Pacific Islanders (309.6 per 100,000), and American Indians/Alaska Natives (294.8 per 100,000).

Yet the enrolment rate in clinical trials for all cancers is 1.8% for whites, 1.3% for both blacks and Hispanics, 1.7% for Asians/Pacific Islanders, and 2.5% for American Indians/Alaska Natives.

  • The percentages of clinical-trial reports that include usable data on racial/ethnic minority populations are “less than optimal”.

The research team’s PubMed searches unearthed five publications reporting on reviews of papers that specified minority participation in clinical trials (all types, not just cancer).

 These publications showed a growing trend towards including reports by race/ethnicity, from 1.5% of the articles specifying race or ethnicity in a 1997 review to 57% in 2011. In the latter review, though, only 36% of the articles provided any analysis by racial or ethnic groups.

  • Barriers to minority participation in cancer clinical trials persist, such as mistrust, costs, transportation and differences in cultural perspectives.

Other barriers, Chen et al note, include lack of awareness about available trials, physician neglect in inviting patients to consider study participation, linguistic barriers, and trial-design characteristics.

  • Evidence is accumulating on the growing value of participation in cancer clinical trials.  

For example, molecular characterisation of tumours from patients treated with the EGFR tyrosine kinase inhibitor gefitinib has shown not only that tumours with epidermal growth factor-receptor mutations are highly sensitive to gefitinib but that the proportion of patients with EGFR-mutant tumors is higher in Asian populations than in other racial groups.

This finding enabled rapid completion of a large randomised study (the IRESSA Pan-Asia Study trial) conducted predominately in Asian countries, which demonstrated the superiority of gefitinib over standard chemotherapy in patients with advanced lung cancer harbouring an EGFR mutation and revolutionised the treatment of lung cancer worldwide.

Deliberate effort

“The proportion of minorities in clinical research remains very low and is not representative of the US population with cancer,” commented Chen, who is associate director for cancer control at the UC Davis Comprehensive Cancer Center.

“What is needed is deliberate effort,” he added. “Minorities are not hard to reach. They are hardly reached.”

Among the research team’s recommendations are that journal editors should require appropriate representation and analyses of NIH-funded research by race/ethnicity; and that the NCI should prioritise new clinical trials based on adequacy of sampling specific to individual groups rather than organ sites.