After receiving abnormal results on a flexible sigmoidoscopy screening test, more than 25 percent of participants in a large national trial did not go to a doctor for the recommended follow-up test, a diagnostic colonoscopy. Blacks in the study were less likely than whites to have the follow-up colonoscopy, according to a study published online April 6 in the Journal of the National Cancer Institute.
Previous studies have suggested that blacks are at greater risk for colorectal cancer and have a higher mortality rate than whites, but it is unclear whether this disparity is due to biological differences or differences in access to health care. No study has examined racial disparity in colorectal cancer according to both health care utilization and the results of screening.
To look at this question, Adeyinka O. Laiyemo, M.D., of the Division of Cancer Prevention, National Cancer Institute, Bethesda, Md., and colleagues used data from the ongoing Prostate, Lung, Colorectal, and Ovarian Cancer Screening (PLCO) Trial. A total of 60,572 African-American and non-Hispanic white participants in this study underwent flexible sigmoidoscopy screening in ten centers across the United States from November 1993 to July 2001. This initial screening found suspicious lesions in similar percentages of blacks and whites (25.5% vs 23.9%).
Of those screened, 13,743 white and 767 black men and women were referred to their own physicians for a diagnostic colonoscopy. The PLCO did not pay for the follow-up visits. Of those referred, 9,944 (72.4%) whites and 480 (62.6%) blacks went on to see a physician and have a colonoscopy.
The researchers also reviewed the colonoscopy results for these 10,424 subjects. No statistically significant difference between blacks and whites was found in the prevalence of polyps, advanced adenomas, advanced pathology in small adenomas, or colorectal cancer.
"We did not observe any meaningful differences in the yield of colorectal cancer neoplasia by race," the authors write. "We observed a lower rate of diagnostic evaluation following an abnormal screening among blacks as compared with whites." Taken together, the two findings "suggest that the biology of colorectal cancer may not be materially different by race, at least in the early stages of carcinogenesis, but instead that healthcare utilization differences among the races may play a more important role in the observed disparities in colorectal cancer."
In an accompanying editorial, John Z. Ayanian, M.D., M.P.P., of Harvard Medical School, Boston, says the study "identified an important barrier to optimal care--follow-up of abnormal findings on sigmoidoscopy--that affected many white participants and an even larger proportion of black participants."
He notes that "colorectal cancer is one important disease in which racial and socioeconomic disparities in outcomes can most readily be eliminated by ensuring that all eligible adults are effectively screened and abnormal findings are fully treated."
Study limitations: Only participants with lesions in the distal colon would be identified by flexible sigmoidoscopy screening.
Contacts:
Article: Adeyinka O. Laiyemo, M.D., NCI Press Office, (301) 496-6641, ncipressofficers@mail.nih.gov
Editorial: John Z. Ayanian, M.D., ayanian@hcp.med.harvard.edu
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