Gastroenterology

Gastroenterology

Volume 158, Issue 2, January 2020, Pages 354-367
Gastroenterology

Review
Causes of Socioeconomic Disparities in Colorectal Cancer and Intervention Framework and Strategies

https://doi.org/10.1053/j.gastro.2019.10.029Get rights and content

Colorectal cancer (CRC) disproportionately affects people from low socioeconomic backgrounds and some racial minorities. Disparities in CRC incidence and outcomes might result from differences in exposure to risk factors such as unhealthy diet and sedentary lifestyle; limited access to risk-reducing behaviors such as chemoprevention, screening, and follow-up of abnormal test results; or lack of access to high-quality treatment resources. These factors operate at the individual, provider, health system, community, and policy levels to perpetuate CRC disparities. However, CRC disparities can be eliminated. Addressing the complex factors that contribute to development and progression of CRC with multicomponent, adaptive interventions, at multiple levels of the care continuum, can reduce gaps in mortality. These might be addressed with a combination of health care and community-based interventions and policy changes that promote healthy behaviors and ensure access to high-quality and effective measures for CRC prevention, diagnosis, and treatment. Improving resources and coordinating efforts in communities where people of low socioeconomic status live and work would increase access to evidence-based interventions. Research is also needed to understand the role and potential mechanisms by which factors in diet, intestinal microbiome, and/or inflammation contribute to differences in colorectal carcinogenesis. Studies of large cohorts with diverse populations are needed to identify epidemiologic and molecular factors that contribute to CRC development in different populations.

Section snippets

Socioeconomic Features of CRC Disparities

SES is one of the strongest and most consistent predictors of health, overall disease burden, and premature death. One study found larger socioeconomic disparities in risk for overall mortality among healthy people than in people with poor self-rated health.10 CRC outcomes are also socioeconomically patterned. People with low SES have poorer outcomes throughout the entire CRC care continuum, with reasons ranging from differences in risk factors (such as dietary and other behavioral factors)11,12

Explanations for Socioeconomic Disparities in CRC

Evidence from observational and experimental studies offer plausible explanations for SES disparities and could provide guidance for interventions. Socioeconomic measures are related to social determinants of health: conditions people are exposed to during their life course that are shaped by the distribution of money, power, and resources.22,23 Within that context, the relation of SES to health outcomes can be conceptualized as the social or economic position of individuals or populations that

Features of CRC That Associate With Disparities

There are few data on racial/ethnic differences in molecular features of colorectal tumors because most published studies come from cohorts of almost exclusively NHW patients.37 Only recently have publications addressed potentially differentiating factors.38

Adenomas are the direct precursors to most CRCs, with advanced adenomas the most proximate to CRC onset.39,40 Studies of adenomas might therefore provide insight to the mechanisms of CRC disparities and potential interventions. As for CRC,

Diet, the Intestinal Microbiome, and CRC Disparities

Interactions between diet and the intestinal microbiome might contribute to CRC disparities. There is increasing evidence that diet and composition of the intestinal microbiome affect risk of adenoma and CRC.8,65, 66, 67 Adenomas develop from aberrant crypt foci, which are the earliest detectable neoplastic growths in the colon.39,40 They are presumed to result from local environmental effects on stem cells within colonic crypts, which induce mutations and neoplasia via alterations in the Wnt

Interventions

Strategies to reduce disparities in CRC incidence and mortality should aim to reduce risk of CRC and improve detection and treatment. Interventions have generally focused on increasing access to existing health services. However, less attention has been paid to improving community resources as an essential component of enabling access to evidence-based interventions (EBI) for CRC health promotion, screening, diagnosis, and treatment.

EBIs to improve screening participation can reduce or

Future Directions

Disparities persist in CRC incidence and mortality despite national efforts: AAs have the highest rates among all racial and ethnic groups in the United States. Low SES is associated with higher rates of CRC, and might contribute to changes in the colon, via lifestyle factors such as diet. Diets high in fat and red meat and low in fiber can alter the intestinal microbiome, promote inflammation, and disrupt immune surveillance to contribute to initiation and progression of CRC (Figure 3).

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    Conflicts of interest The authors disclose no conflicts.

    Funding This work was supported by the US Public Health Service (R01 CA206010 to JMC and R01CA213645 and R37CA222866 to CAD) and the A. Alfred Taubman Medical Research Institute of the University of Michigan (to JMC). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.

    ∗

    Authors share co-first authorship.

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