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

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.