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Guideline-recommended colorectal screening may miss cancer in patients at increased risk
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First-degree relatives of patients with colorectal adenomas or advanced adenomas are at increased risk for colorectal neoplasia, but screenings performed based on current guidelines may miss 10% of these cancers, according to results of a population-based, retrospective, case-control study.
The analysis included 126,936 adults aged 50 to 80 years who underwent colonoscopy between 1995 and 2009 at Intermountain Healthcare or the University of Utah.
The case population included 43,189 patients who had an adenomatous polyp removed, including 5,563 with advanced adenomas. The case patients were matched by sex and birth year with controls who underwent colonoscopy but were free of adenomas or colorectal cancer.
First-degree relatives of patients with adenomas (RR=1.35; 95% CI, 1.25-1.46) and advanced adenomas (RR=1.68; 95% CI, 1.29-2.18) were at increased risk for colorectal cancer compared with relatives of controls.
Researchers also found that first-degree relatives with adenomas (RR=1.33; 95% CI, 1.26-1.4) and advanced adenomas (RR=1.65; 95% CI, 1.28-2.14) were likely to have a similar polyp to that of the index patient.
Second-degree relatives of patients with adenomas were at a significantly increased risk (RR=1.15; 95% CI, 1.07-1.23) for colorectal cancer. Third-degree relatives also were at increased risk for colorectal cancer (RR=1.06; 95% CI, 1-1.12), but the difference was not statistically significant.
Second- and third-degree relatives of patients with advanced adenomas did not have an increased risk for colorectal cancer.
Researchers also stratified results by age of case patients at the time of diagnosis of colorectal neoplasia. Compared with relatives of controls, the risk for colorectal cancer was slightly more significant in first- and second-degree relatives of patients with adenomas diagnosed at age 59 or younger (RR=1.41; 95% CI, 1.27-1.56) than those diagnosed at age 60 or older (RR=1.23; 95% CI, 1.07-1.42).
Using these age-adjusted analyses, researchers determined 10% of colorectal cancer incidences in patients younger than 60 years would have been missed under current screening guidelines. The guidelines recommend colonoscopy screening in first-degree relatives starting at age 40 years, or 10 years before the index patient.
“Our results support the current screening guidelines, but they also raise the issue of whether some level of more aggressive screening should be considered, not only for first-degree relatives of patients with polyps diagnosed at or below age 60, but also for those first-degree relatives of patients diagnosed above age 60,” researcher N. Jewel Samadder, MD, MSc, of Huntsman Cancer Institute at the University of Utah, said in a press release. “To validate other components of the current screening guidelines, we need to continue with a more in-depth examination of the risk of colorectal cancer in relatives of patients diagnosed with colorectal cancer or advanced adenomas, looking at factors such as the size of the polyp, the degree of cell abnormality and location of the tumor in the bowel.”
Disclosure: Researchers report consultant and speakers’ bureau roles with Cook Medical Inc. and Myriad Genetics.
Perspective
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Tanios Bekaii-Saab, MD
Tuohy and colleagues demonstrated that the presence of adenomas on patients’ colonoscopies might indicate an elevated risk of developing colorectal cancer (CRC) in their relatives. This measured to 10% of CRCs being missed in relatives if there was strict adherence to current guidelines. These broad findings are consistent with some previously published studies that suggest an increased risk of developing CRC in relatives of patients with colorectal adenomas. This study and others are limited by their retrospective nature. Further limitations to this study are the lack of cost-effectiveness and survival benefit analyses. In other words, will subjecting relatives of patients with adenomas to colonoscopies justify the cost and the potential benefit? The results of this study are certainly interesting, but they should not lead to a change in today’s guidelines until many of the questions raised have been addressed prospectively.
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