Racial and Ethnic Disparities in Interval Colorectal Cancer Incidence: A Population-Based Cohort Study

Abstract

Background: Interval colorectal cancer (CRC) accounts for 3% to 8% of all cases of CRC in the United States. Data on interval CRC by race/ethnicity are scant.

Objective: To examine whether risk for interval CRC among Medicare patients differs by race/ethnicity and whether this potential variation is accounted for by differences in the quality of colonoscopy, as measured by physicians' polyp detection rate (PDR).

Design: Population-based cohort study.

Setting: Medicare program.

Participants: Patients aged 66 to 75 years who received colonoscopy between 2002 and 2011 and were followed through 2013.

Measurements: Kaplan-Meier curves and adjusted Cox models were used to estimate cumulative probabilities and hazard ratios (HRs) of interval CRC, defined as a CRC diagnosis 6 to 59 months after colonoscopy.

Results: There were 2735 cases of interval CRC identified over 235 146 person-years of follow-up. A higher proportion of black persons (52.8%) than white persons (46.2%) received colonoscopy from physicians with a lower PDR. This rate was significantly associated with interval CRC risk. The probability of interval CRC by the end of follow-up was 7.1% in black persons and 5.8% in white persons. Compared with white persons, black persons had significantly higher risk for interval CRC (HR, 1.31 [95% CI, 1.13 to 1.51]); the disparity was more pronounced for cancer of the rectum (HR, 1.70 [CI, 1.25 to 2.31]) and distal colon (HR, 1.45 [CI, 1.00 to 2.11]) than for cancer of the proximal colon (HR, 1.17 [CI, 0.96 to 1.42]). Adjustment for PDR did not alter HRs by race/ethnicity, but differences between black persons and white persons were greater among physicians with higher PDRs.

Limitation: Colonoscopy and polypectomy were identified by using billing codes.

Conclusion: Among elderly Medicare enrollees, the risk for interval CRC was higher in black persons than in white persons; the difference was more pronounced for cancer of the distal colon and rectum and for physicians with higher PDRs.

Primary funding source: American Cancer Society.

Figure 1

Cohort Selection Criteria, SEER-Medicare 2002–2011 Abbreviations: Surveillance Epidemiology and End Results (SEER), Colorectal Cancer (CRC)

Figure 2

Cumulative Probability of Interval Colorectal Cancer by Race/Ethnicity, SEER-Medicare 2002–2011* Abbreviations: Surveillance Epidemiology and End Results (SEER), Colorectal Cancer (CRC) *Log Rank p-value <0.001