Gut microbiome and cancer
Gathering this level of granular data is crucial because health disparities can be driven by both biological and social determinants, Li said. Knowing more about people's ancestry may give them an edge when it comes to fending off cancer, not just with regard to inherited cancer mutations but in terms of biology, like the way our bodies responds to the foods we eat.
Case in point: blacks and colorectal cancer.
As Li and his co-authors point out in their new paper, research has shown that African-Americans living in the U.S. have a high risk for colorectal cancer, whereas blacks who live in rural South Africa do not. In the U.S., 65 out of every 100,000 people are diagnosed; in South Africa, it's less than five out of 100,000. These disparities have primarily been associated with diet (blacks in the U.S. eat more animal fat and less fiber), but an international study, published in 2015, offered further insights.
The scientists recruited participants from both groups, gathered samples of their gut microbiota — that teeming community of bacteria, viruses and other microorganisms that helps our bodies break down food and can influence our risk for diseases like cancer — then swapped their diets: the African-Americans ate a typical high-fiber South African diet, and the South Africans switched to a typical U.S. diet with high meat and fat intake.
Within two weeks, Li said, "they saw a complete shift in the gut microbiome." The South Africans' microbiome developed the same markers for cancer risk that the African-Americans originally had, and the African-Americans' gut microbiomes reflected a drop in the cancer risk markers. And as soon as the two groups returned to their normal diets, the gut microbiomes slipped back to what they were originally.
"This shows the dynamic nature of the microbiome, how sensitive it is to diet and how those diets could affect colon cancer incidence," Li said. "There's a lot more research to be done but it points to trying to identify why we see different patterns of cancer in populations that have similar genetic ancestry and how potentially modifiable exposures like diet can have a real impact on cancer risk."
Research that reaches everybody
Another strong recommendation from the new joint statement: redesign cancer clinical trials to acknowledge and address cancer disparities.
According to statistics from the National Institute on Minority Health and Health Disparities, Hispanic and Latino Americans make up less than 8 percent of enrollees in clinical trials, even though they make up 17 percent of the population. African-Americans represent 13.2 percent of the total U.S. population, but the FDA cites a 5 percent involvement in trials. All told, non-whites make up less than 5 percent of participants in clinical trials supported by the National Institutes of Health.
As a result, researchers aren't able to gather valuable data on how minorities respond to potential new therapies (not everyone responds the same), and minority patients aren't able to access new treatments that could potentially save or improve their lives.
Fear and mistrust of doctors is part of the problem (the Tuskegee Syphilis Study still haunts many), but there are other factors at play. Clinical trials are often conducted at large research institutions or hospitals so may not be as accessible to rural residents. Individual trial criteria can sometimes exclude patients, such as those with additional health issues or "comorbidities" like obesity, diabetes and/or other cancers (more commonplace in blacks). Underserved groups and/or or non-English speakers may not hear about studies in time to enroll or may have to drop out early due to economic constraints. Medical centers that serve minority patients may not have the capacity to support all the activities associated with conducting trials, such as providing more frequent exams and collecting more blood and tissue samples.
The four organizations called for a number of strategies to remedy these issues:
- Increased minority involvement in study design, particularly when it comes to determining who can enroll;
- Longer recruitment periods so underrepresented populations have a chance to hear about new trials;
- Better relationships between researchers and community health advisors who work with underserved populations
- More community-engaged research.