Background: It is unclear whether the higher rate of colorectal cancer (CRC) among non-Hispanic blacks (blacks) is due to lower rates of CRC screening or greater biologic risk.
Objective: We aimed to evaluate whether blacks are more likely than non-Hispanic whites (whites) to develop distal colon neoplasia (adenoma and/or cancer) after negative flexible sigmoidoscopy (FSG).
Design: We analyzed data of participants with negative FSGs at baseline in the Prostate, Lung, Colorectal, and Ovarian (PLCO) cancer screening trial who underwent repeat FSGs 3 or 5 years later. Subjects with polyps or masses were referred to their physicians for diagnostic colonoscopy. We collected and reviewed the records of diagnostic evaluations.
Participants: Our analytic cohort consisted of 21,550 whites and 975 blacks.
Main measures: We did a comparison by race (whites vs. blacks) in the findings of polyps or masses at repeat FSG, the follow-up of abnormal test results and the detection of colorectal neoplasia at diagnostic colonoscopy.
Key results: At the follow-up FSG examination, 304 blacks (31.2 %) and 4183 whites (19.4 %) had abnormal FSG, [adjusted relative risk (RR) = 1.00; 95 % confidence interval (CI), 0.90-1.10]. However, blacks were less likely to undergo diagnostic colonoscopy (76.6 % vs. 83.1 %; RR = 0.90; 95 % CI, 0.84-0.96). Among all included patients, blacks had similar risk of any distal adenoma (RR = 0.86; 95 % CI, 0.65-1.14) and distal advanced adenoma (RR = 1.01; 95 % CI, 0.60-1.68). Similar results were obtained when we restricted our analysis to compliant subjects who underwent diagnostic colonoscopy (RR = 1.01; 95 % CI, 0.80-1.29) for any distal adenoma and (RR = 1.18; 95 % CI, 0.73-1.92) for distal advanced adenoma.
Conclusions: We did not find any differences between blacks and whites in the risk of distal colorectal adenoma 3-5 years after negative FSG. However, follow-up evaluations were lower among blacks.
Keywords: PLCO; adenomatous polyps; colorectal cancer disparities; flexible sigmoidoscopy; screening.