麻豆传媒

A diverse international panel has released new risk-based recommendations on colorectal cancer (CRC) screening in asymptomatic, previously unscreened individuals ages 50 to 79 with a life expectancy of at least 15 years.

The document, published in , makes the following recommendations, which the 21-member panel categorized as "weak":

• No screening for individuals with an estimated 15-year CRC risk below 3% – the threshold above which the balance of benefits and harms tilts in favor of screening

• For individuals with an estimated 15-year CRC risk above 3%, screening with fecal immunochemical testing (FIT) every year; FIT every 2 years; a single sigmoidoscopy; or a single colonoscopy

The recommendations and the process that led to them are presented in easy-to-follow color infographics.

The panelists, led by Lise M. Helsingen, MD, of Oslo University Hospital in Norway, explained that they made the recommendations in light of recent of sigmoidoscopy screening trials that provided new evidence about the effectiveness of CRC screening.

Helsingen and co-authors said that they used a linked systematic review of trials and microsimulation modeling estimates of 15-year screening benefits and harms. The team also reviewed each screening option's practical issues and burdens, and then estimated the magnitude of benefit that typical members of the population would need to perceive in order to opt for screening; the authors then used the benefit thresholds to inform their recommendations.

The authors acknowledged several limitations to determining the benefit thresholds -- for example, having to rely on indirect evidence and their own experience in making their estimates, since no direct evidence so far exists.

The panel said that based on the benefits, harms, and burdens of screening, the group's conclusion was that most informed individuals with a 15-year risk of colorectal cancer of at least 3% are likely to choose screening, while most with a risk below 3% are likely to decide not to have screening.

And whichever is chosen, "given varying values and preferences, optimal care will require shared decision-making," the authors emphasized.

They also suggested using the to estimate CRC risk. This online instrument factors in age, sex, ethnicity, smoking status, alcohol use, family history of gastrointestinal cancer, personal history of other cancers, diabetes, ulcerative colitis, colonic polyps, and body mass index.

For the future, further clarification is needed about the general population's values and preferences regarding the magnitude of benefit needed for individuals to undergo screening and with which screening test, the authors said. Other questions worth exploring, they said, are the benefits and harms of colonoscopy versus FIT screening and any effects that might differ between men and women.

'Seismic Shift'

Writing in an , with the subtitle "A radical shift that prioritizes informed choice over maximizing uptake," Philippe Autier, MD, MPH, PhD, of the International Prevention Research Institute in Lyon, France, noted the "seismic shift" toward risk-based screening as the best way to discuss cancer screening with .

He pointed, however, to the panel's conclusion that the evidence for CRC "is still fragile, and strong recommendations cannot yet be issued." The group's work, Autier continued, would have been less complicated had results from randomized trials of FIT and colonoscopy screening been available.

Autier also cited the need for new research to refine screening recommendations. He said that if the goal of screening is to reduce mortality by preventing late-stage disease, "better knowledge of risk factors associated with late stage at diagnosis and colorectal cancer death is likely to improve risk-based approaches."

The current CRC of the U.S. Preventive Services Task Force (USPSTF) recommend screening for all individuals ages 50 through 75, and note that select individuals ages 76 to 85 should be screened only if their risk factors and history warrant it, and that those older than 85 should not be screened.

As to the best screening method, USPSTF vice chair Alex Krist, MD, MPH, of Virginia Commonwealth University in Richmond, who was not a member of the panel for the BMJ recommendations, told MedPage Today: "All tests are equally effective in reducing deaths. It's a matter of personal preference. The best test is the one that a person gets."

A recent report from the International Agency for Research on Cancer confirmed that screening sigmoidoscopy, colonoscopy, and fecal tests can all reduce deaths from CRC.