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Average-risk individuals may benefit from screening tools other than colonoscopy
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A clinical scoring test designed to determine risk for advanced neoplasia may help practitioners identify individuals who can safely consider non-colonoscopy approaches for colorectal cancer screening, according to the results of a cross-sectional study.
This type of risk stratification could enable clinicians to tailor screening methods so those at lower risk can undergo less invasive tests — such as sigmoidoscopy or occult blood tests — and those at higher risk can undergo colonoscopy.
“The natural history of colorectal neoplasia, which usually involves a slow progression from precancerous polyp to cancer, lends itself to screening,” Thomas F. Imperiale, MD, professor of medicine at Indiana University, and colleagues wrote. “Despite the favorable biology, test options and evidence to support screening, it is underused, costly and inefficient.”
Thomas F. Imperiale
About 22 million Americans aged 50 to 75 years have never undergone colorectal cancer screening, and only about two-thirds have undergone lower endoscopy of any type in the past decade, researchers wrote. Screening also often is inefficient.
“Low-risk persons may receive colonoscopy with low yield and little benefit, and high-risk persons may receive noninvasive testing with missed opportunity for benefit,” Imperiale and colleagues wrote. “Tailoring of colorectal cancer screening based on risk could improve the overall uptake and efficiency of screening.”
Imperiale and colleagues used the most common risk factors for colorectal neoplasia to create a risk index for advanced neoplasia — defined as colorectal cancer and adenomas or serrated polyps 1 cm or larger, those with villous histology or high-grade dysplasia — anywhere in the colorectum.
Researchers assigned point values for each risk factor, including age (0 points for < 55 years, 1 point for 55 to <60 years, 2 points for 60 to < 65 years, 3 points for 65 to < 70 years, and 4 points for ≥ 70 years); sex (0 for women and 1 for men); waist circumference (0 for small, 1 for medium and 2 for large); history of cigarette smoking (0 for zero pack-years, 2 for > 0 to < 30 pack-years, and 4 for ≥ 30 pack years); and family history of colorectal cancer (1 for first-degree relative with colorectal cancer and 0 for other).
The researchers used the scores to divide individuals into four groups — very low risk, low risk, intermediate risk and high risk.
Imperiale and colleagues evaluated the risk index in a cross-sectional study of individuals who underwent initial colonoscopy screening between December 2004 and September 2011. The final analysis included data from a derivation cohort (n = 2,993; mean age, 57.3 years) and a validation cohort (n = 1,467; mean age, 57.2 years).
In the derivation cohort, the researchers observed a 9.4% prevalence of advanced neoplasia. They determined risks for advanced neoplasia were 1.92% (95% CI, 0.63-4.43) among individuals at very low risk; 4.88% (95% CI, 3.79-6.18) among those classified as low risk; 9.93% (95% CI, 8.09-12) among those classified as intermediate risk; and 24.9% (95% CI, 21.1-29.1) among those classified as high risk (P < .001 for trend).
Fifty-three percent of individuals (n = 1,591) were in the low or very low risk groups. Researchers identified five cancers — all located in the distal colon — in this subgroup. Sigmoidoscopy to the descending colon in the low-risk groups would have detected 51 of 70 advanced neoplasms (73%; 95% CI, 61-83).
Imperiale and colleagues observed similar risks for advanced neoplasia in the validation cohort.
In this group, slightly more than half (53%.5; n = 786) were classified as low risk or very low risk. The researchers did not detect any cancers in this subgroup. Also, 21 of 24 advanced neoplasms (87.5%; 95% CI, 68-97) would have been detected using sigmoidoscopy with subsequent colonoscopy for a finding of a distal polyp.
The researchers acknowledged several study limitations, including the reliance on published literature to determine risk index factors and the imperfect discrimination of the prediction equation. Further, whites comprised 94% of the study cohort, even though blacks are believed to be at higher risk for colorectal neoplasia.
“The index identified both lower-risk groups that may be screened with strategies other than colonoscopy and a higher-risk group for which colonoscopy may be preferable in terms of yield and efficiency,” Imperiale and colleagues concluded. “If this index is further validated externally in independent cohorts, it could increase the uptake and efficiency of colorectal cancer screening in the U.S.”
Chyke A. Doubeni
The risk index may serve as an advisory tool but should not preclude colonoscopy in all average-risk patients, Chyke A. Doubeni, MD, MPH, presidential professor of family medicine and community health at University of Pennsylvania’s Perelman School of Medicine, wrote in an accompanying editorial.
“[The study] demonstrates the use of simple clinical information for prediction of colorectal neoplasia risk,” Doubeni wrote. “The score may be useful in counseling average-risk patients about their risk for colorectal cancer. But until stronger scientific evidence is available, I would not recommended such scores for choosing the type of screening test an average-risk person should have. …
“Improved risk stratification of patients currently classified as average risk remains an important scientific and policy aspiration,” Doubeni added. “Until high-performing tools are available, the best approach to optimize screening is to provide patients the best test they are willing and able to complete with high fidelity.” – by Cameron Kelsall
Disclosure: Imperiale reports grants from NCI, Walther Cancer Foundation, Indiana Clinical and Translational Sciences Institute, and Indiana University Melvin and Bren Simon Cancer Center. The other researchers report no relevant financial disclosures. Doubeni reports no relevant financial disclosures.
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