Tool Could Limit Invasive Colorectal Cancer Screening

Yael Waknine

August 10, 2015

Scientists have developed a five-variable index aimed at identifying which individuals in the average-risk spectrum for advanced colorectal neoplasia (ACN) can skip colonoscopy in favor of less invasive screening. The researchers report the results of their cross-sectional study in an article published online August 11 in Annals of Internal Medicine, but at least one expert cautions against using the new tool.

"Tailoring of colorectal cancer screening based on risk could improve the overall uptake and efficiency of screening. For lower-risk persons within the average-risk group, screening could be done with stool-based occult blood tests or sigmoidoscopy (or both), which are less invasive, less risky, and less costly than colonoscopy," write Thomas F. Imperiale, MD, from the Regenstrief Institute at the Indiana University Medical Center in Indianapolis, and colleagues.

For the study, investigators enrolled 4460 patients scheduled for a first colonoscopy between December 2004 and September 2011, assigning them in a 2:1 ratio to derivation (n = 2993) and validation (n = 1467) sets; 94% of participants were white.

Points for the risk assessment score were assigned on the basis of age (0 points for <55 years, 1 for 55 to <60 years, 2 for 60 to <65 years, 3 for 65 to <70 years, 4 for ≥70 years), male sex (1 point), presence of first-degree relative with colorectal cancer (1 point), smoking history (0 points for nonsmoker; 2 for >0 to <30 pack-years; 4 for ≥30 pack-years), and waist circumference (0 points for small, 1 for medium, 2 for large).

Tallies ranged from 0 to 13 and were stratified into 4 ACN risk groups: very low (0), low (1 to 3), intermediate (4 to 6), and high (7 to 12).

Colonoscopy findings in the derivation set supported the model, with ACN rates ranging from 1.92% (95% confidence interval [CI], 0.63% - 4.43%) and 4.88% (95% CI, 3.79% - 6.18%) in the very low and low-risk groups to 24.9% (95% CI, 21.1% - 29.1%) in the high-risk group (P < .001).

In the validation set, ACN rates ranged from 1.65% (95% CI, 0.20% - 5.84%) and 3.31% (95% CI, 2.08% - 4.97%) for very low-risk and low-risk individuals, compared with 22.3% (95% CI, 16.9% - 28.5%) among those at high risk (P < 0.001).

"Use of sigmoidoscopy alone in the low-risk groups would have detected 73% to 87.5% of all advanced neoplasia in a single application," the authors point out.

Risk Stratification Score Better Limited to Follow-up Use

"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 recommend such scores for choosing the type of screening test an average-risk person should have," cautions Chyke A. Doubeni, MD, MPH, from the University of Pennsylvania Perelman School of Medicine in Philadelphia, in an accompanying editorial.

"The use of risk algorithms for individualized selection of screening tests is itself a form of screening and thus requires a relatively high level of sensitivity across diverse populations to be safely used in clinical decision making," Dr Doubeni writes. He notes that that the study's derivation model also lacked sensitivity, only modestly discriminating between patients with ACN and those without (c-statistic = 0.72).

Moreover, the colonoscopy alternatives mentioned by the authors are not necessarily viable — sigmoidoscopy is not commonly used in the United States and fecal immunochemical tests detect only about 25% of ACN cases.

"[U]ntil 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," Dr Doubeni emphasizes.

However, a sensitive algorithm based on strong empirical evidence may potentially prove useful in guiding follow-up measures for a negative screening result, Dr Doubeni concludes.

The study was funded by the National Cancer Institute, Walther Cancer Institute, Indiana University Simon Cancer Center, and Indiana Clinical and Translational Sciences Institute. Dr Imperiale reports grants from the National Cancer Institute, Walther Cancer Foundation, Indiana Clinical and Translational Sciences Institute, and Indiana University Melvin and Bren Simon Cancer Center during the conduct of the study. The authors have disclosed no other relevant financial relationships.

Ann Intern Med. Published online August 11, 2015. Abstract Editorial

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