Guidelines

New practice guideline: CRC screening isn’t necessary for low-risk patients aged 50-75 years

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Current models that predict risk lack precision

There is compelling evidence that CRC screening of average-risk individuals is effective – screening with one of several modalities can reduce CRC incidence and mortality in average-risk individuals. Various guidelines throughout the world have recommended screening, usually beginning at age 50 years, in a one-size-fits-all manner. Despite our knowledge that different people have a different lifetime risk of CRC, no prior guidelines have suggested that risk stratification be built into the decision making.

Dr. David Lieberman, Oregon Health and Science University, Portland

Dr. David Lieberman

A new clinical practice guideline from an international panel applies principles of precision medicine to CRC screening and proposes a paradigm shift by recommending screening to higher-risk individuals, and not recommending screening if the risk of CRC is low. Intuitively, this makes sense and conserves resources – if we can accurately determine risk of CRC. This guideline uses a calculator (QCancer) derived from United Kingdom data to estimate 15-year risk of CRC. The panel suggests that for screening to be initiated there should be a certain level of benefit: a CRC mortality or incidence reduction of 5 per 1,000 screenees for a noninvasive test like fecal immunochemical test (FIT) and a reduction of 10 per 1,000 screenees for invasive tests like sigmoidoscopy and colonoscopy. When these estimates of benefit are placed into a microsimulation model, the cutoff for recommending screening is a 3% risk of CRC over the next 15 years. This approach would largely eliminate any screening before age 60 years, based on the calculator rating, unless there is a family history of GI cancer.

All of the recommendations in this practice guideline are weak because they are derived from models that lack adequate precision. Nevertheless, the authors have proposed a new approach to CRC screening, similar to management plans for patients with cardiovascular disease. Before adopting such an approach, we need to be more comfortable with the precision of the risk estimates. These estimates, derived entirely from demographic and clinical information, may be enhanced by genomic data to achieve more precision. Further data on the willingness of the public to accept no screening if their risk is below a certain threshold needs to be evaluated. Despite these issues, the guideline presents a provocative approach which demands our attention.

David Lieberman, MD, AGAF, is professor of medicine and chief of the division of gastroenterology and hepatology, Oregon Health & Science University, Portland. He is President of the AGA Institute.


 

FROM BMJ

Patients 50-79 years old with a demonstrably low risk of developing the disease within 15 years probably don’t need to be screened for colorectal cancer. But if their risk of disease is at least 3% over 15 years, patients should be screened, Lise M. Helsingen, MD, and colleagues wrote in BMJ (2019;367:l5515 doi: 10.1136/bmj.l5515).

For these patients, “We suggest screening with one of the four screening options: fecal immunochemical test (FIT) every year, FIT every 2 years, a single sigmoidoscopy, or a single colonoscopy,” wrote Dr. Helsingen of the University of Oslo, and her team.

She chaired a 22-member international panel that developed a collaborative effort from the MAGIC research and innovation program as a part of the BMJ Rapid Recommendations project. The team reviewed 12 research papers comprising almost 1.4 million patients from Denmark, Italy, the Netherlands, Norway, Poland, Spain, Sweden, the United Kingdom, and the United States. Follow-up ranged from 0 to 19.5 years for colorectal cancer incidence and up to 30 years for mortality.

Because of the dearth of relevant data in some studies, however, the projected outcomes had to be simulated, with benefits and harms calculations based on 100% screening adherence. However, the team noted, it’s impossible to achieve complete adherence. Most studies of colorectal screening don’t exceed a 50% adherence level.

“All the modeling data are of low certainty. It is a useful indication, but there is a high chance that new evidence will show a smaller or larger benefit, which in turn may alter these recommendations.”

Compared with no screening, all four screening models reduced the risk of colorectal cancer mortality to a similar level.

  • FIT every year, 59%.
  • FIT every 2 years, 50%.
  • Single sigmoidoscopy, 52%.
  • Single colonoscopy, 67%.

Screening had less of an impact on reducing the incidence of colorectal cancer:

  • FIT every 2 years, 0.05%.
  • FIT every year, 0.15%.
  • Single sigmoidoscopy, 27%.
  • Single colonoscopy, 34%.

The panel also assessed potential harms. Among almost 1 million patients, the colonoscopy-related mortality rate was 0.03 per 1,000 procedures. The perforation rate was 0.8 per 1,000 colonoscopies after a positive fecal test, and 1.4 per 1,000 screened with sigmoidoscopy. The bleeding rate was 1.9 per 1,000 colonoscopies performed after a positive fecal test, and 3-4 per 1,000 screened with sigmoidoscopy.

Successful implementation of these recommendations hinges on accurate risk assessment, however. The team recommended the QCancer platform as “one of the best performing models for both men and women.”

The calculator includes 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.

“We suggest this model because it is available as an online calculator; includes only risk factors available in routine health care; has been validated in a population separate from the derivation population; has reasonable discriminatory ability; and has a good fit between predicted and observed outcomes. In addition, it is the only online risk calculator we know of that predicts risk over a 15-year time horizon.”

The team stressed that their recommendations can’t be applied to all patients. Because evidence for both screening recommendations was weak – largely because of the dearth of supporting data – patients and physicians should cocreate a personalized screening plan.

“Several factors influence individuals’ decisions whether to be screened, even when they are presented with the same information,” the authors said. These include variation in an individual’s values and preferences, a close balance of benefits versus harms and burdens, and personal preference.

“Some individuals may value a minimally invasive test such as FIT, and the possibility of invasive screening with colonoscopy might put them off screening altogether. Those who most value preventing colorectal cancer or avoiding repeated testing are likely to choose sigmoidoscopy or colonoscopy.”

The authors had no financial conflicts of interest.

SOURCE: BMJ 2019;367:l5515. doi: 10.1136/bmj.l5515.

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