Individuals from certain areas of the United States are more likely to get screened for colorectal cancer than those from other areas, particularly when comparing non-whites living in different parts of the country. That is the conclusion of a new study published early online in Cancer, a peer-reviewed journal of the American Cancer Society. Additional research is needed to better understand how colorectal cancer screening disparities develop in some regions and not in others.

Racial and ethnic disparities in colorectal screening exist among the Medicare population, but researchers do not know whether these disparities differ across geographic regions. To find out, Thomas Semrad, MD, of the University of California Davis led a team that examined colorectal cancer screening among Medicare enrollees within eight U.S. states. Individuals were considered up-to-date on screening if they had fecal occult blood testing in the prior year or sigmoidoscopy or colonoscopy in the prior five years.

There was little geographic variation in up-to-date status among whites, who were consistently more likely to be up-to-date on screening than other races (except in Hawaii). White versus non-white up-to-date status varied significantly across regions for blacks and Asian/Pacific Islanders but not Hispanics. While white versus black differences in up-to-date status were greatest in Atlanta, rural Georgia, and the San Francisco Bay Area (range: 10 percent to 16 percent differences), there were no significant white versus black differences in Connecticut, Seattle, or Iowa. Whereas Asian/Pacific Islanders had significantly lower up-to-date prevalence than whites in Michigan, San Francisco, Los Angeles, and San Jose (range: 4 percent to 15 percent differences), Asian/Pacific Islanders in Hawaii had higher up-to-date status than whites (52 percent versus 38 percent). White versus Hispanic differences were substantial but homogeneous across regions (range: 8 percent to 16 percent differences).

The authors concluded that variations in racial and ethnic disparities in colorectal cancer testing among Medicare patients stems principally from regional differences in testing among non-whites. "This finding highlights the need to understand the regional determinants of health care provision for non-white groups," said Dr. Semrad. He noted that the overall proportion of Medicare enrollees who are up-to-date on colorectal cancer screening remains poor and that significant work needs to be done to improve overall screening rates in addition to closing disparities in screening rates amongst racial and ethnic groups.