Residence in ethnic enclaves associated with reduced breast, colorectal cancer risk among Asians, Hispanics

Living in ethnically or racially segregated neighborhoods appeared associated with a reduced risk for breast and colorectal cancers among Asian or Hispanic patients, but an increased risk for cancers with infectious origins, study data showed.

“Prior published studies suggest that the ‘social environment’ (eg, the physical and social setting in which people live) may be related to various cancer outcomes, such as cancer risk or mortality,” Carolyn Fang, PhD, co-leader of cancer prevention and control and professor at Fox Chase Cancer Center in Philadelphia, told HemOnc Today. “Ethnic density (often defined as the proportion of racial/ethnic minority individuals who reside in a given geographic area) is one of the most frequently studied social environment factors, but the findings on ethnic density and cancer have been somewhat mixed.”

Fang and Marylin Tseng, PhD, of the kinesiology department at California Polytechnic State University used PubMed to identify 51 studies focusing on the relationship of ethnic density and racial segregation with cancer.

Most studies included in the analysis examined ethnic density only among Hispanic or Asian-American residents. Further, all but one study measured ethnic composition instead of racial segregation. Only six studies focused on ethnic density of black neighborhoods.

In general, ethnic density appeared associated with an increased lifetime risk for cancer in Asian or Hispanic neighborhoods. These neighborhoods had a higher incidence of cancers with infectious origins — including cervical and liver cancers — but a lower incidence of colorectal and breast cancers.

Researchers did not have enough data on black neighborhoods to draw any conclusions about these cancers.

When Fang and Tseng evaluated cancer stage at diagnosis, the studies reported mixed results for black neighborhoods, with no association between black-white segregation and cancer stage in one study, positive associations between segregation and cancer stage in two studies and an inverse association between segregation and stage of breast or colorectal cancer in two more studies.

However, studies of predominantly Hispanic neighborhoods appeared more consistent, with all studies quantifying ethnic density of Hispanic residents demonstrating positive links between ethnic density and later stage at diagnosis of melanoma and breast, cervical and colorectal cancers.

In general, patients who lived in neighborhoods with a high density of black residents appeared more likely to die of colorectal or breast cancer, regardless of whether they were black or white.

The researchers wrote that living in ethnic enclave may help preserve healthy cultural norms, such as the consumption of low-fat diets in Asian-American and Hispanic neighborhoods, but could also reinforce cultural beliefs that negatively impact cancer screening.

“It is hoped that these findings will create greater awareness that broader factors, such as the social environment, could be associated with cancer risk or outcomes,” Fang said. “This awareness may also lead to advances in how we address racial and ethnic disparities in cancer.” – by Andy Polhamus

Disclosures: The authors report no relevant financial disclosures.