Individualized genetic and environmental risk assessment of susceptibility to colorectal cancer does not influence adherence to screening in average-risk persons, according to results from a two-group, randomized, controlled trial. Among patients who received genetic and environmental risk assessment and those who did not, approximately one-third completed colorectal screening during the 6-month follow-up. “These findings raise concern about the effectiveness of moderately predictive assessment of genetic risk to promote favorable health care behavior,” David S. Weinberg, MD, MSc, of Fox Chase Cancer Center, Philadelphia, and colleagues stated in the Annals of Medicine.
“Unlike with genetic testing for high-risk persons, such as those with familial adenomatous polyposis, little is known about the impact on health behaviors or the psychological effects of providing average-risk persons with moderately predictive genetic information,” the authors wrote. “Understanding the benefits and harms of such testing in average-risk persons is important because similar testing is marketed directly to the public in an unsupervised fashion.”
The study involved 783 participants from four medical school–affiliated primary care practices. At the time they entered the study, the participants were considered at average risk for colorectal cancer but were not adherent to colorectal cancer screening recommendations. Average risk was defined as “being asymptomatic and having no personal history of colorectal adenomas, cancer, or inflammatory bowel disease or no family history of familial adenomatous polyposis, hereditary nonpolyposis colorectal cancer, or colorectal cancer in a first-degree relative.” Nonadherence to colorectal cancer screening guidelines was defined as “not having had home fecal occult blood testing in the past 12 months, barium enema or flexible sigmoidoscopy in the past 5 years, or colonoscopy in the past 10 years.”
Participants completed baseline surveys of demographic characteristics, multivitamin use, and psychometric and knowledge characteristics. There were no significant differences in any of these variables between participants randomly assigned to usual care or genetic and environmental risk assessment. Most patients were aged 50 to 59, and 56% were white.
In addition to the baseline survey, patients assigned to genetic and environmental risk assessment met with a specially trained nurse to discuss the purpose of genetic and environmental risk assessment. These participants were told that their results would be classified as average or elevated, but that “an average result did not ensure protection against colorectal cancer now or in the future” and an elevated result “did not guarantee disease but was only one potential risk factor for colorectal cancer, suggesting modestly increased risk compared with that of a similarly aged person.” The study nurse emphasized that genetic and environmental risk assessment was not intended to be a substitute for screening.
Genetic and environmental risk assessment “evaluated methylenetetrahydrofolate reductase polymorphisms and serum folate levels. On the basis of prespecified combinations of polymorphisms and serum folate levels, genetic and environmental risk assessment recipients were told that they were at elevated or average risk for colorectal cancer,” the researchers explained.
The primary outcome of the study was colorectal cancer screening within 6 months of entering the study. “Overall screening rates for colorectal cancer did not statistically significantly differ between the usual care (35.7%) and genetic and environmental risk assessment (33.1%) groups. After adjustment for baseline participant factors, the odds ratio for screening completion for genetic and environmental risk assessment vs usual care was 0.88 (95% confidence interval [CI], 0.64–1.22),” the researchers reported.
Within the genetic and environmental risk assessment group, screening rates did not significantly differ between average-risk (38.1%) and elevated-risk (26.9%) participants. Odds ratios for elevated-risk vs average-risk participants remained nonsignificant after adjustment for covariates (odds ratio [OR], 0.75 [CI, 0.39–1.42]).”
The researchers also investigated whether baseline factors may have confounded their results. “Black participants were significantly more likely than white participants to be at elevated risk, presumably because of well-described differences in allele distribution frequency across race (OR, 5.92 [CI, 3.26–10.74]),” the researchers noted. “That regular multivitamin use was significantly inversely associated with elevated-risk status (OR, 0.24 [CI, 0.13–0.44]) was also expected, because regular multivitamin users may have higher serum folate levels.”
Other significant differences included generally lower education levels in the elevated-risk group and less baseline knowledge about colorectal cancer screening and genetics and diet. Using a multivariate logistic model to adjust for potential confounding did not alter the conclusion that genetic and environmental risk assessment risk classification had no significant effect on screening.
Although feedback from a single personalized genetic and environmental risk assessment was not positively associated with colorectal cancer screening in average-risk persons, the investigators noted that “additional studies will be required to evaluate whether other approaches to providing genetic and environmental risk assessment affect screening utilization differently.”
“We should not look toward personalized medicine and genomics to refine risk estimates in ways that will, on their own, motivate substantial behavior change,” according to an editorial accompanying the article. “Instead, we should utilize such information to identify patients who are most in need of such screening and then rely on proven persuasion techniques to encourage patients to undergo screening (for example, default screening appointments and videos that make the harms of not screening salient). The editorial was written by J. S. Blumenthal-Barby, PhD, MA, and Amy L. McGuire, JD, PhD, Center for Medical Ethics and Health Policy, Baylor College of Medicine, Houston, and Peter A. Ubel, MD, Fuqua School of Business and Sanford School of Public Policy, Duke University, Durham, North Carolina. ■
Weinberg DS, et al: Ann Intern Med 161:537-545, 2014.
Blumenthal-Barby JS, McGuire AL, Ubel PA: Ann Intern Med 161:605-606, 2014.