By Marina Shayevich

Why do African Americans develop breast cancers with significantly higher basal gene expression? ¹ Why do Hispanics develop type II diabetes at an earlier age than other groups? ² Understanding the functional reasons for disease processes is necessary to develop targeted treatments. Yet because clinical research lacks sufficient diversity, reasons for and mechanisms of disease development are not fully understood.

Some reasons for minority patient under-representation in clinical trials are known. For example, strict eligibility criteria, like chronic kidney disease,³ hypertension or diabetes exclusions, leave out many groups, specifically minority populations, with higher prevalence of these diseases.

Income can reduce the likelihood of participation in clinical trials. In one study, participants with an annual income of less than $50,000 had 32% lower odds of having participated in a clinical trial than higher income patients.⁴ Census data show that the median household income for whites is $65,000, African Americans is $38,000 and Hispanics $45,000.⁵

Other documented causes related to income, such as childcare and travel, can interfere with participation. Though the cost of the tested medication is free in clinical trials, there may be added medications that must be covered by insurance. Those without adequate coverage may be less likely to participate.

Moreover, historically unscrupulous experiments conducted on minorities, like the Tuskegee study, also impact interest and trust in research participation.

Why diversity matters

Although there is variability in self-reported race and ethnicity, research that has focused on self-reported diverse populations have found surprising reasons for varied treatment outcomes. For example, African-American and Puerto Rican children have the highest prevalence of asthma in the US and it has been observed that albuterol, a commonly prescribed bronchodilator inhalant, is less effective in these children than Caucasians. A recent study found that these children have a genetic variant in the NFKB1 gene, present in people of African ancestry, which impacts factors like lung volume and immune responses making albuterol less likely to work. ⁶

Another clinical research study compared self-identified African American and Caucasian men with metastatic castrate-resistant prostate cancer. The medication was more effective in African American men. African American participants treated with the hormonal therapy had lower PSAs for longer periods of time than their Caucasian counterparts. The groups also had differences in side effects; the Caucasian participants experienced fatigue more, while African American participants experienced potassium deficiencies in their blood.⁷

According to the American Cancer Association, African Americans have the highest death rates and shortest survival rates of most cancers among ethnic groups in the US. ⁸A recent study looked at genetic expression data in breast cancer tumor samples from both African American and Caucasian women. African Americans had significantly more TP53 mutations than Caucasian tumor samples. The samples also had significantly higher triple negative and basal molecular subtypes.¹ Knowing how these genetic expressions impact treatment and finding ways to address these differences must be part of future breast cancer research.

But, for people fighting cancer right now, there are more pressing reasons for concern about being left out of cancer clinical trials, like immunotherapy. As Judy Perkins, the first person cured of metastatic breast cancer with immunotherapy, told Inspire, people who are metastatic run out of conventional treatments. For her, going from clinical trial to clinical trial was the only option in terms of prolonging her life. How many desperately ill minorities who have exhausted other treatment options are missing out on early access to experimental drugs that could improve their quality of life or extend their lives?

To learn what diverse patients and caregivers think about clinical trials, Inspire conducted virtual patient interviews. This Thursday February 21, I will present the findings from these interviews in a free Inspire webinar, “Diversity in Clinical Trials: Understanding Patient and Caregiver Perspectives at 2pm ET, 1pm CT and 11am PT. Click here to sign up.