Led by Rachel B. Issaka, MD, of Fred Hutchinson Cancer Center, Seattle, the Clinical Practice Update focuses primarily on time frames for surveillance based on known risk factors, plus a caution against widespread use of emerging risk-stratification tools that need more real-world evidence among diverse populations.
“Based on current evidence, risk stratification for initiating CRC screening or surveillance should be based on age, family history, predisposing hereditary CRC syndromes, prior screening, or other CRC predisposing conditions,” the authors wrote in Gastroenterology.
Dr. Rachel B. Issaka
With these parameters in mind, Dr. Issaka and colleagues issued nine best practice advice statements, noting that systematic reviews were not conducted, so statements are not rated based on quality of evidence or strength of presented considerations.
To begin, the investigators characterized two risk strata for CRC. Individuals with a first-degree relative who was diagnosed with CRC have an increased risk of CRC, particularly if that relative was diagnosed before age 50. In contrast, people with no such family history, or a personal history of CRC, hereditary CRC syndromes, inflammatory bowel disease, or other predisposing conditions, have average risk for CRC.
Those with average risk should start CRC screening at age 45, while those with high risk should start screening at age 40, or 10 years before the age of diagnosis of their youngest affected relative, whichever is sooner.
“The age to initiate screening according to family history of CRC could be optimized based on the number of affected family members, age at diagnosis of the affected relatives, as well as the 10-year cumulative incidence of CRC according to age within a specific source population (e.g., country),” the investigators wrote. “However, in the absence of widely available risk calculators developed for such risk-adapted screenings, a simplified approach to consider is initiating screening approximately 10 years before the age of diagnosis of the youngest affected relative or at age 40 years.”
The decision to screen and conduct postpolypectomy surveillance beyond age 75 should factor in risks, benefits, screening history, and comorbidities.
According to Dr. Issaka and colleagues, individuals with average risk can choose between several options for screening based on preference and availability, including fecal immunochemical test, colonoscopy, flexible sigmoidoscopy plus fecal immunochemical test, multitarget stool DNA fecal immunochemical test, and computed tomography colonography. Those with high risk, however, should undergo colonoscopy.
The final best practice advice statement offers a word of caution against widespread use of new risk-stratification tools for CRC and postpolypectomy surveillance that have yet to demonstrate real-world effectiveness and cost-effectiveness in diverse populations.
“Validation within diverse racial and ethnic populations is critical for models that include genetic factors, because genetic discovery studies have focused largely on individuals with European ancestry, and because risk-relevant genetic factors may vary according to individual’s origin of genetic ancestry,” the investigators wrote. “Although many studies differentiate individuals by race and ethnicity, which may capture some information about the likely presence of certain genetic variants, ancestry is a better predictor and should be captured in validation studies.”
The update was commissioned and approved by the AGA, and supported by the National Cancer Institute of the National Institutes of Health. The investigators disclosed relationships with Geneoscopy, CellMax Life, Universal Diagnostics, and others.
