TUESDAY, Feb. 13 (HealthDay News) -- Even though U.S. Medicare has expanded coverage for colon cancer screening, blacks and Hispanics are not benefiting as much as whites, a new study shows.

Researchers at the Medical College of Wisconsin analyzed 2002-2003 data on nearly 600,000 Medicare patients in New York, Florida and Illinois. Overall, about 18.3 percent of those people were screened for colorectal cancer during the study period.

"Blacks (9.7 percent) and Hispanics (8.1 percent) had lower rates of colon cancer screening compared with whites (19.3 percent)," the study authors wrote in the Feb. 12 issue of the journal Archives of Internal Medicine.

The poor were also less likely to get screened. "Individuals living in ZIP codes with a higher per capita income were more likely to undergo a colon screening test than were those living in ZIP codes with a lower per capita income (21 percent and 14.6 percent in the highest and lowest tertiles, respectively)."

Rates varied by state, as well. The study found that 21.5 percent of the study participants in Florida had been screened, compared with 16.6 percent in Illinois and 16.2 percent in New York.

The researchers also found that people who lived in a ZIP code with a greater amount of high school graduates were more likely to have colon cancer screening and that women were less likely than men to undergo an invasive screening test or colonoscopy.

"Further research is needed to determine the basis for the observed ongoing disparities to develop interventions to reduce and eliminate these differences," the study authors concluded.

In the United States, colorectal cancer is the third most common kind of cancer. About 145,290 cases of colorectal cancer were diagnosed in the country in 2005, according to background information in the study.

"There is evidence that screening for colorectal cancer decreases incidence and mortality from the disease," the study authors noted.

More information

The U.S. National Cancer Institute has more about colorectal cancer screening.