Interval cancer after screening colonoscopy more common in black patients than in white patients

Adjusting for the physicians' detection rate did not alter the differences in risk associated with race/ethnicity, the study noted.

Black patients were more likely than white patients to be diagnosed with colorectal cancer between screening colonoscopies, a recent study found.

The population-based cohort study included Medicare patients ages 65 to 75 years who received screening colonoscopies between 2002 and 2011. They were followed through 2013 to determine whether risk for interval cancer differed by race or ethnicity and, if so, whether the disparity was explained by the quality of colonoscopy, measured by physicians' polyp detection rates. Results were published in the May 23 Annals of Internal Medicine.

In the 235,146 person-years of follow-up, there were 2,735 cases of interval colorectal cancer, defined as cancer diagnosed after a negative screening colonoscopy but before the time of the recommended next screening colonoscopy. Black patients were more likely than white ones to receive colonoscopy from a physician with a low polyp detection rate (52.8% vs. 46.2%). A low detection rate was significantly associated with interval cancer risk, and 7.1% of black patients had interval cancers, compared to 5.8% of white patients. The hazard ratio (HR) for interval cancer in black patients compared to white patients was 1.31 (95% CI, 1.13 to 1.51), and the disparity was greater in rectal cancer (HR, 1.70; 95% CI, 1.25 to 2.31) and distal colon cancer (HR, 1.45; 95% CI, 1.00 to 2.11) than in proximal cancer (HR, 1.17; 95% CI, 0.96 to 1.42).

However, adjusting for the physicians' detection rate did not alter the differences in risk associated with race/ethnicity. The study did find greater differences in cancer risk between black and white patients when both were screened by physicians with high detection rates. The findings align with previous observations of disparities appearing with higher-quality or new medical interventions, the authors noted. “Whether this finding is attributable to physician factors, including lower quality of examination, is unknown and warrants exploration,” they wrote.

Aspects of care quality other than the polyp detection rate might contribute to the observed disparities, the authors noted. There could also be unmeasured differences in the speed at which the cancers developed and adherence to recommended screenings. Further research is needed, including about the quality of colorectal cancer screening for black patients and the potential utility of race-specific surveillance colonoscopy recommendations, the authors said.