After a Clear Colonoscopy, Can Screening Intervals Be Extended and How Much Does Cancer Risk Fall?

Findings supporting an extension of rescreening intervals after a negative colonoscopy for colorectal cancer screening to more than 10 years were reported in a study published on 27 November 2024 in JAMA Oncology. Knudsen and colleagues noted that this proposal is particularly relevant for people with a low-risk profile.

• What Is a Colonoscopy? Why and How Is It Performed?

Colonoscopy is recommended for both men and women after age 45. This screening method allows the inside of the colon and rectum (large intestine) to be visualized. Colonoscopy is one of the most effective methods doctors use to:

• Look for polyps in the colon .
• Identify the cause of bowel symptoms
• Colon and rectal  cancer screening  / early detection

Details of the Recent JAMA Study

This US cohort study used data from three prospective US population-based cohorts of nurses and health professionals: the Nurses' Health Study, Nurses' Health Study II, and Health Professionals Follow-up Study. Follow-up began in 1988 and 1991 and continued through 2020. Data from the National Health and Nutrition Examination Survey (NHANES), covering 1 January 2017 to 31 December 2018, were also used to compare the distribution of risk profiles with that of the general US population.

A total of 195,453 participants (median age: 44; 81% women) were followed for a median of 12 years (interquartile range: 6–20 years). Among 81,151 people with negative screening colonoscopy results, 394 developed colorectal cancer and 167 died from it. Among 114,302 people who did not undergo screening colonoscopy, 2,229 developed colorectal cancer and 637 died from it.

What the Findings Mean

Negative colonoscopy results were consistently associated with lower colorectal cancer incidence (hazard ratio [HR] = 0.51; 95% confidence interval [CI]: 0.44–0.58) and colorectal cancer mortality (HR = 0.56; 95% CI: 0.46–0.70) over 20 years of follow-up.

Among people with negative colonoscopy results, the 10-year cumulative incidence of colorectal cancer was 0.78% in those with a high risk score. This level was reached after 16 years in those with an intermediate risk score and after 25 years in those with a low risk score.

Who Is at Low or High Risk of Colorectal Cancer?

For colorectal cancer, low- and high-risk profiles are defined according to factors affecting a person's likelihood of developing cancer. Genetic, environmental, lifestyle, and medical-history factors are considered in defining risk profiles.

Low-Risk Profile

• Family History: No family history of colorectal cancer or adenomatous polyps.
• Age: Generally, people younger than 50, although this age cutoff may vary according to clinical guidelines.
• Lifestyle Factors:
  • A healthy, balanced diet (high in fiber and low in red and processed meat).
  • A physically active lifestyle.
  • No excessive alcohol consumption and no smoking.
• Medical History:
  • No previous bowel disease, such as inflammatory bowel disease.
  • A negative colonoscopy or a clear screening history.
  • No adenomatous or hyperplastic polyps.
• Other Factors: A body mass index (BMI) within the normal range and no history of diabetes.

High-Risk Profile

• Genetic Factors:
  • Hereditary cancer syndromes such as Lynch syndrome (Hereditary Nonpolyposis Colorectal Cancer - HNPCC) or Familial Adenomatous Polyposis (FAP).
  • A history of colorectal cancer or adenomatous polyps in first-degree relatives (parents, siblings).
• Age: People aged 50 and older (some guidelines use 45 as the threshold for increased risk).
• Medical History:
  • Previous colorectal cancer.
  • A diagnosis of inflammatory bowel disease, such as Crohn's disease or ulcerative colitis.
  • Adenomatous polyps detected on a previous colonoscopy.
• Lifestyle Factors:
  • High consumption of red and processed meat.
  • Smoking and excessive alcohol use.
  • A sedentary lifestyle.
• Other Factors: Overweight or obesity, diabetes, and low vitamin D levels.

Managing Risk Factors

• Low-Risk Individuals: Screening intervals can be longer, for example, 10 years.
• High-Risk Individuals: More frequent screening, consideration of genetic testing, and lifestyle changes are recommended. Screening in these people may begin at age 40 or earlier.

These definitions offer general guidance, but each person's risk assessment should be tailored to their personal and family history.

Interpretation of the Results

This study highlights the importance of negative screening colonoscopy results and their role in shared decision-making between patients and physicians. The findings suggest that, for people with a low-risk profile, it may be reasonable to consider extending rescreening intervals beyond the current 10-year recommendations. This provides a basis for individualized approaches to screening strategies.

The study also reinforces the vital importance of considering colorectal cancer risk factors in rescreening decisions. Tailoring screening intervals to risk profiles may help avoid unnecessarily frequent screening and use screening resources more effectively. These findings provide important proof of concept that individual risk assessments should be an integral part of screening programs.