Elderly black patients on Medicare are at a 31% higher risk for colorectal cancer (CRC) than white patients, according to a study done by Stacey A. Fedewa, PhD, MPH, and her colleagues at the American Cancer Society.

There were 2,735 cases of interval CRC identified between 2002 and 2011 for this study. The patients studied were between 66 and 75 years of age and were all enrolled in Medicare. A higher proportion of black individuals, 52.8%, received a colonoscopy from physicians with a lower polyp detection rate (PDR, a proxy for adenoma detection rate), compared with whites at 46.2%. The PDR, the number of patients in whom a polypectomy is performed divided by the number of colonoscopies performed in a 5-year period, is significantly associated with interval CRC risk (Ann Intern Med. 2017. doi: 10.7326/M16-1154).

Interval CRC, defined as cancer that develops after a negative result on colonoscopy but before the next recommended test, accounts for 3%-8% of CRC cases in the United States. These cases of CRC develop in certain populations because they were missed at the time of screening or between recommended screenings or surveillance intervals.

Results showed that the probability of interval CRC by the end of follow-up was 7.1% in blacks, 5.8% in whites, 4.4% in Hispanics, and 3.8% in Asians. Of the 79,396 Medicare patients that met enrollment criteria, 61,433 were included in the study. The average age of index colonoscopy was 70 years, and 2,735 cases of interval CRC were identified.

“Future studies examining this issue are warranted, given the higher overall risk for interval CRC in black populations as well as the larger disease burden in this group,” Dr. Fedewa said.

Medicare patient data were gathered from the National Cancer Institute’s Surveillance, Epidemiology, and End Results program (SEER), a data collection of 18 cancer registries across the United States. Claims data were used to identify receipt and dates of patient colonoscopies and polypectomies, as well as the PDR of administering physicians. Data from SEER was used to identify cases of interval CRC. Medicare Enrollment data were used to determine patients’ ethnicities.

The primary exposures were ethnicity and physician PDR, a relative measure of colonoscopy quality. Ethnicities were categorized as non-Hispanic white, black, Hispanic, Asian, and other. Patients were followed until they died, were no longer enrolled in Medicare, or experienced interval CRC defined as a first case of primary invasive CRC diagnosed 6-59 months after the colonoscopy.


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