Study Identifies Racial Disparity in Risk of Interval Colorectal Cancer

A study published in the Annals of Internal Medicine reports that black Medicare enrollees are less likely to receive colonoscopy from more highly-rated physicians, which could increase their risk for interval colorectal cancer (CRC), a cancer that develops after a colonoscopy but prior to the next recommended test.

Guidelines in the United States recommend screening for CRC beginning at age 50 in both men and women, based on their average risk for the disease. Screening reduces incidence and mortality by catching precancerous lesions early enough at disease onset and increases the probability of better outcomes. Accounting for nearly 8% of new cancer cases in the United States, CRC was most prevalent among black men in 2013.

Interval CRCs, which make up 3% to 8% of CRC cases in the United States, may stem from patient demographics, clinical factors, and physician factors, including quality of colonoscopy metrics. However, race has not yet been identified as a risk factor for interval CRC.

For their current study, the authors wanted to examine race as a risk factor for interval CRC and its association with the quality of colonoscopy, measured by the physicians’ polyp detection rate (PDR) metric.

The authors identified 2735 interval CRC cases among patients 66 to 75 years of age in the National Cancer Institute's Surveillance, Epidemiology, and End Results (SEER) program, who had a colonoscopy between 2002 and 2011. PDR was the surrogate measure for quality, with a high PDR indicative of better quality of colonoscopy.

The study found that 52.8% of black individuals in the study received a colonoscopy from physicians with a low PDR, compared with 46.2% of white persons, with an interval CRC of 7.1% and 5.8%, respectively. PDR, the authors note, was significantly associated with an interval cancer. Black persons in the group had a significantly higher risk for interval CRC (Hazard ratio [HR], 1.31; 95% CI, 1.13 to 1.51). with the greatest disparity observed for rectal cancer (HR, 1.70; 95% CI, 1.25 to 2.31) and the distal colon (HR, 1.45; 95% CI, 1.00 to 2.11).

Compared with whites, blacks had a 31% higher risk for interval CRC after accounting for polyp detection rate and factors such as socioeconomic status. Differences between black persons and white persons were greater among physicians with higher PDRs, the authors write.

“Our findings are consistent with previous reports that blacks were more likely to receive healthcare from physicians in lower resource settings and also experienced poorer outcomes,” said Stacey Fedewa, PhD, MPH, of the American Cancer Society, who led the study. She concluded that interventions that improve outcomes for patients can increase disparities, since they’re often less available to ethnic minorities.

Reference

Fedewa SA, Flanders WD, Ward KC, et al. Racial and ethnic disparities in interval colorectal cancer incidence: a population-based cohort study [published online May 23, 2017]. Ann Intern Med. 2017. doi: 10.7326/M16-1154.