The risk for interval colorectal cancer (CRC), or CRC that develops after a negative result on a colonoscopy but before the next recommended screening, is much higher in older black patients than in those of any other race or ethnicity, a new study concludes.
Interval CRC accounts for 3% to 8% of all cases of CRC in the United States, the authors note.
Their study was intended see whether the risk for interval CRC varied by ethnicity, and they found that it did – by a whopping 31% in blacks vs whites.
The overall risk for interval CRC was 7.1% for Medicare enrollees who were African American compared to 5.8% for their white counterparts (hazard ratio [HR], 1.31), according to a research team led by Stacey Fedewa, MD, PhD, strategic director of risk factors and screening surveillance at the American Cancer Society in Atlanta, Georgia.
These disparities were more pronounced for cancers of the distal colon and rectum (HR, 1.45 and 1.70, respectively) than for cancer of the proximal colon (HR, 1.17), the study authors say in a report published online May 22 in the Annals of Internal Medicine.
An increased risk for interval CRC was also seen in black patients screened by physicians whose rates for detecting polyps was higher. However, a higher proportion of black patients (52.8%) than white patients (46.2%) underwent colonoscopy performed by physicians with a lower of detecting polyps. The polyp detection rate (PDR) is a surrogate measure for the quality of colonoscopy significantly associated with interval CRC risk.
Adjustment for PDR did not alter HRs by race/ethnicity. “Whether this finding is attributable to physician factors, including lower quality of examination, is unknown and warrants exploration,” Dr Fedewa and colleagues say.
The study also shows that Asian patients had significantly lower risk for interval CRC than white patients (HR, 0.72), a finding consistent with the lower overall incidence of CRC previously reported in this group. There was no significant difference in interval CRC risk between Hispanic persons and white persons.
“Our findings and those reported elsewhere highlight the importance of attentive examination of the colon and rectum during colonoscopy to achieve the optimal benefit of this test,” Dr Fedewa told Medscape Medical News. “These 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.”
This study is “one of the first to examine the issue of racial/ethnic disparities in interval colorectal [cancer],” she emphasized. But she does not believe it is time to make changes in guidelines or clinical practice. “Given the higher overall risk for interval CRC in black populations as well as the larger disease burden in this group, we need to dig a little deeper into some of our findings with more detailed investigation.”
Study Details
For the study, Medicare claims files linked to data from the National Cancer Institute’s Surveillance, Epidemiology, and End Results (SEER) program were examined for interval CRC in 61,433 patients. Participants ranged in age from 66 to 75 years at the time of colonoscopy. The colonoscopies were performed between 2002 and 2011. Interval CRC occurring 6 to 59 months after colonoscopy was diagnosed in 3294 patients by 4357 unique physicians. Follow-up ended in December 2013, after a maximum of 59 months.
Most colonoscopies were performed by physicians whose primary specialty was gastroenterology, the study showed. The percentage of persons receiving screening colonoscopy was similar in black (79.5%) and white patients (80.7%), as were polypectomy rates at index colonoscopy (23.4% and 24.7%, respectively).
The study did not directly assess whether or not the higher rates of interval CRCs in black patients were due to higher rates of unavoidable de novo cancers, Dr Fedewa pointed out. “Our results, along with others, provide some evidence that this might not be case.”
A review of studies that examined the effectiveness of physician training on improving quality of colonoscopy metrics indicated mixed results, she said. “Before eliminating disparities, we would first need to know how to improve quality and if such programs would eliminate disparities.”
When asked to comment, Jean S. Wang, MD, PhD, associate professor of medicine at Washington University School of Medicine in St. Louis, Missouri, said that when it comes to access to healthcare, effective mechanisms for leveling the playing field are already in place, but more could be done. Unequal access to healthcare is “the most significant factor driving this higher risk for interval colon cancer in black patients,” she noted in an email.
“US clinicians should mandate that all physicians providing colonoscopy services are providing high-quality care and are tracking their adenoma detection rates to ensure that they are exceeding minimum quality standards,” Dr Wang told Medscape Medical News.
Patient navigation programs can also help patients manage the often complicated process of CRC screening, she said. “When equal access has been implemented on a city-wide or system-wide basis, such as in New York City or [in] the Veterans Affairs system, racial and ethnic disparities in colon cancer are significantly reduced.”
Dr Wang pointed out that this study confirms that black patients are more likely to undergo colonoscopies by clinicians with lower PDRs. This correlates with adenoma detection rates and reflects technical skill, she said. Low PDRs can be a red flag for missed cancer.
“Next steps would be to evaluate other factors associated with high-quality colonoscopy, such as cecal intubation rates — a measure of the completeness of colonoscopy —withdrawal time, and adequacy of bowel preparation to see how these factors may contribute to the racial and ethnic disparities seen in interval colon cancer,” Dr Wang said.
This study was funded by the American Cancer Society. The authors and Dr Wang have disclosed no relevant financial relationships.
Ann Intern Med. Published online May 22, 2017. Abstract
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