New research from UC Davis Cancer Center has found that whether a person gets screened for colon cancer often depends on where they live in addition to their race or ethnicity.

It has long been known that racial minorities have lower colorectal screening rates than whites, presumably because of differences in socioeconomic status, access to care and cultural issues. What hasn’t been known, until now, is whether these differences also vary across geographic regions.

In a paper published online today in the journal Cancer, medical oncologist Thomas Semrad and colleagues at UC Davis Cancer Center demonstrate that while screening rates for whites rarely vary regardless of geography, location accounts for significant differences in colorectal testing among non-whites.

Semrad and his team analyzed data from 53,990 Medicare enrollees ages 69 to 79 in eight states and 11 regions including: Atlanta, Ga.; rural Georgia; San Francisco-Oakland; San Jose-Monterey; Los Angeles County; Seattle-Puget Sound, Wash.; Detroit, Mich.; Connecticut; Hawaii; Iowa; and New Mexico.

Individuals were considered up-to-date on colon cancer screening if they had a colonoscopy or sigmoidoscopy within the prior five years or fecal occult blood testing within the past year. The researchers controlled for sociodemographic, medical and environmental factors that could affect regional differences in colorectal cancer screening.

What they found was that whites were more likely to be up-to-date on screening than other races everywhere, except in Hawaii, where Asian-Pacific Islanders had significantly higher screening rates than whites (52 percent versus 38 percent).

“This is a stunning finding,” said Semrad. “Screening rates among Asians in Hawaii were the highest of any group in any cancer registry area, including whites.”

Semrad suspects that a potential explanation is the influence of Japanese culture in Hawaii. Since other gastrointestinal cancers are prevalent in the Japanese population, he said, there may be more awareness of the benefits of screening.

Geography also played a significant role in screening rate variations among African Americans, Semrad found. For example, in the state of Iowa, African Americans and whites had nearly identical screening rates, suggesting that access to screening is similar and that providers are recommending screening to Medicare enrollees regardless of their race or ethnicity.

The same was not true in the city of San Jose, Calif., where whites had similar screening rates to whites in Iowa (45 percent), but where screening rates among African Americans (29 percent) were among the lowest found in the study.

Researchers also found substantial disparities when comparing white and Hispanic screening rates in all regions that had substantial Hispanic populations. But unlike the Asian and African-American groups, there was virtually no difference in screening rates among Hispanics in the different regions.

Explaining the geographic variations in screening rates among non-whites will require much more detailed research, Semrad said. But he suspects that non-whites in some regions may be segregated within primary care practices and health systems that may be less likely to provide colorectal cancer screening. Less access to primary care and to gastrointestinal specialists also may play a significant role in these variations.

A possible explanation of variation among Asian-Pacific Islanders is ethnicity and cultural differences that may influence attitudes toward preventive care and cancer screening, Semrad said. Other research shows that Chinese immigrants in Seattle, for example, may opt for more traditional methods such as maintenance of energy (qi) and spririt (jing shen), exercise and diet for prevention rather than medical screening.

“The next step is to look at different geographic areas to see what are the determinants for minorities in terms of getting screened,” said Semrad. “Are these culturally based? Are there problems with how health-care systems are set up? What are the barriers? If we can figure this out, we would have a target to improve some of these disparities.”

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The research was funded with an American Cancer Society Mentored Research Scholars grant to Joshua Fenton, assistant professor of Family and Community Medicine and a member of the UC Davis Center for Healthcare Policy and Research.

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Contact: Dorsey Griffith
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University of California - Davis Health System