Blacks have a higher prevalence of colon polyps compared to whites and their tumors are harder to detect, as they are located higher in the colon, US researchers said.

Colon cancer is the second leading cause of cancer death in the US and the third most common type of cancer. Colorectal cancer claims about 56,000 lives every year. The American Cancer Society estimates almost 150,000 new cases of colorectal cancer for 2008 in the US.

According to a study in the September 24 issue of The Journal of the American Medical Association, African-Americans develop colon cancer more often and die from it more often compared to whites. Death rates for black men and women are 38 percent to 43 percent higher than for white men and women, and incidence rates are 15.5 percent to 23 percent higher in black individuals.

When trying to explain the reasons behind these figures, the study authors said “colorectal cancer screening might be less effective in black individuals, if there are racial differences in the age-adjusted prevalence and location of cancer precursor lesions.”

Studying nearly 5,500 blacks and more than 80,000 whites who had colonoscopies, David A. Lieberman, M.D., of Portland VA Medical Center, Portland, Ore., and colleagues found that nearly 8 percent of blacks had one or more polyps sized more than 9 millimeters in diameter compared to slightly more than 6 percent of whites.

Another interesting finding of the study was that the tumors in blacks were more likely to be in the upper part of the colon where a sigmoidoscopy would be unlikely to find it. The procedure involves the analysis of the lower half of the colon.

In order to prevent more cases of colon cancer in black people, Dr. Lieberman suggested more screening among this category of people before the age of 50.

“These data strongly emphasize the importance of timely screening in black women and men,” he said.