Among adults at average risk for colorectal cancer who undergo screening colonoscopy, the yield of large polyps and tumors varies widely by patient age, sex, race, and ethnicity. This means that an across-the-board recommendation to initiate screening for all patients at a particular age "may not appear rational and could negatively impact adherence," Dr. David A. Lieberman and his colleagues said in the August issue of Gastroenterology (doi:org/10.1053/j.gastro.2014.04.037).
In what they described as "the largest and most comprehensive analysis of average-risk screening with colonoscopy in the United States," the investigators found that the rate of detecting large (and therefore likely advanced) neoplastic lesions was much higher or lower at any given age, depending on the patient’s sex, race, and ethnicity. So the fact that most practice guidelines uniformly recommend initiating colonoscopy screens at age 50 years doesn’t make sense.
"We believe these data, combined with [those of] prior studies, are compelling enough to consider customization of the initiation age of screening based on the risk of large polyps," said Dr. Lieberman and his associates at Oregon Health & Science University, Portland.
They analyzed information from the Clinical Outcomes Research Initiative database, which includes endoscopy findings from 84 diverse practice settings across the country that are representative of all U.S. community, academic, and Veterans Administration endoscopy centers. They included 327,785 exams of patients aged 40 years and older who were at average risk for colorectal cancer and were screened in 2000 through 2011.
Women accounted for half of the study subjects, except for those examined at VA centers, who were predominately male. The study population was 83.6% white, 5.7% black, and 7.7% Hispanic. More than 95% of the participants were aged 50-79 years.
The outcome of interest was the detection of a polyp or tumor larger than 9 mm. "These large lesions are a surrogate for advanced neoplasia," the investigators said.
The prevalence of large neoplasias rose steadily with increasing age across all races and ethnicities and in both sexes.
Across all age groups, women had a lower prevalence of large polyps than men did, suggesting that the initiation of screening colonoscopy can be safely delayed until age 60 years, at least in white and Hispanic women.
Among men younger than 50 years, the prevalence of large polyps was similar between whites (5.3%) and blacks (5.0%). However, the sample of black men in this age group was small (380 patients), so it is possible that this study was simply underpowered to detect the well-known excess of colorectal neoplasias in younger black men.
The prevalence of large polyps was higher in black men than did white men at all other ages until the age of 70 years, at which point the rates even out. Prevalences were 7.1% vs. 6.2% at 50-54 years, 8.5% vs. 7.4% at 55-59 years, 11.5% vs. 8.6% at 60-64 years, and 12.0% vs. 9.7% at 65-69 years.
Black women had a higher prevalence of large polyps than did white women until age 65 years, when the rates evened out. Prevalences were 5.2% vs. 4.2% at 50-54 years, 6.6% vs. 4.5% at 55-59 years, and 6.9% vs. 5.2% at 60-64 years.
These findings "support intensification of screening in black men and women at age 50 years," Dr. Lieberman and his associates said.
Hispanic men and women had a 25% lower rate of polyps than did whites from age 50 through age 79. This finding suggests that initiation of screening colonoscopy can be delayed in Hispanic men and especially in Hispanic women.
The researchers used white men aged 50-54 years as a reference group to compare rates of detection across the study groups. Screening colonoscopy detected large polyps in 6.2% of white men aged 50-54 years. To achieve a similar yield in Hispanic men or black women, they wouldn’t need to be screened until age 55-59 years. To achieve it in Hispanic women, they wouldn’t need to be screened until age 70-74 years.
This study was supported by the National Institute of Digestive and Kidney Diseases. Dr. Lieberman and his associates reported no relevant financial conflicts of interest.