Racial Differences in Risk of Interval Colorectal Cancer


Key Points

  • Black patients had a 31% greater risk for interval colorectal cancer than white patients.
  • The difference was more pronounced for cancer of the distal colon and rectum and in patients undergoing colonoscopy from higher-quality physicians, as measured by higher polyp detection rates.
  • Interval colorectal cancer accounts for between 3% and 8% of all colorectal cases.

A population-based cohort study by Fedewa et al investigating whether the risk for interval colorectal cancer—defined as cancer that develops after a negative colonoscopy result but before the next recommended screening—varies by race or ethnicity has found that black patients face a 31% higher risk for the cancer than white patients. In addition, the difference was more pronounced for patients with cancer of the distal colon and rectum and for patients of physicians with higher polyp detection rates. According to the study, interval colorectal cancer accounts for between 3% and 8% of all colorectal cases. The study was published in Annals of Internal Medicine.

The researchers examined information from Medicare claims files linked to data from the National Cancer Institute’s Surveillance, Epidemiology, and End Results (SEER) program. The researchers selected patients who were between the ages of 66 and 75 at the time they had a colonoscopy between 2002 and 2011. The study objective was to determine whether the risk for interval colorectal cancer varied by race/ethnicity and whether a physician’s polyp detection rate accounted for the potential differences. Patients were followed until they died, were no longer enrolled in Medicare, or experienced interval colorectal cancer (which was defined as colorectal cancer diagnosed 6 to 59 months after index colonoscopy).

Study Results

The researchers found 2,735 cases of interval colorectal cancer indentified over 235,146 person-years of follow-up. A higher proportion of black patients (52.8%) than white patients (46.2%) received colonoscopy from physicians with a lower polyp detection rate. This rate was significantly associated with interval colorectal cancer risk. The probability of interval colorectal cancer by the end of follow-up was 7.1% in black patients and 5.8% in white patients. Compared with white patients, black patients had a significantly higher risk for interval colorectal cancer (hazard ratio [HR] = 1.31; 95% confidence interval [CI] = 1.13–1.51); the disparity was more pronounced for cancer of the rectum (HR = 1.70; 95% CI = 1.25–2.31) and distal colon (HR = 1.45; 95% CI = 1.00–2.11) than for cancer of the proximal colon (HR = 1.17; 95% CI = 0.96–1.42). Adjustment for polyp detection rate did not alter hazard ratios by race/ethnicity, but differences between black patients and white patients were greater among physicians with higher polyp detection rates.

A limitation of the study is that colonoscopy and polypectomy were identified using billing codes.

More Study Needed

“Although quality of colonoscopy was associated with interval [colorectal cancer], it did not account for the racial disparities. Future studies examining this issue are warranted, given the higher overall risk for interval [colorectal cancer] in black populations as well as the larger disease burden in this group,” concluded the study authors.

Stacey A. Fedewa, PhD, MPH, Director of Screening and Risk Factor Surveillance at the American Cancer Society, is the corresponding author of this study.

Primary funding for this study was provided by the American Cancer Society.

The content in this post has not been reviewed by the American Society of Clinical Oncology, Inc. (ASCO®) and does not necessarily reflect the ideas and opinions of ASCO®.