| Key points of the Guide: |
1. Colorectal cancer screening should begin in asymptomatic adults at average risk at age 50 years. 2. Consider not testing average-risk asymptomatic adults between 45 and 49 years of age. Clinicians should discuss the uncertainty about the benefits and harms of screening in this population. 3. Discontinue colorectal cancer screening in asymptomatic average-risk adults over age 75 or in asymptomatic average-risk adults with a life expectancy of 10 years or less. 4.a A screening test for colorectal cancer should be selected in consultation with your patient based on a discussion of benefits, harms, costs, availability, frequency, and values and preferences. 4.b Clinicians should select between a fecal immunochemistry or a high-sensitivity fecal occult blood test every 2 years, a colonoscopy every 10 years or a flexible sigmoidoscopy every 10 years plus a fecal immunochemical test every 2 years as a screening test. of colorectal cancer. 4.c Do not use stool DNA, CT colonography, capsule endoscopy, urine or serum screening tests for colorectal cancer. |
Colorectal cancer (CRC) is the fourth highest incidence and second highest mortality among cancer types in the United States. Between 2000 and 2019, the incidence of CRC increased slightly in people under 50 years of age, decreased in people 50 to 64 years of age, and decreased most sharply in people 65 years of age and older.
The success of any screening program depends on compliance with the screening strategy (ie, the type and frequency of a test, follow-up testing for abnormal results, and treatment). Benefits accrue from the identification and removal of precancerous lesions or localized cancer that can progress and cause morbidity and mortality. Harms include false positive results, physical and psychological harm, overdiagnosis, overtreatment, and financial costs.
Commonly used screening interventions include stool (fecal immunochemical tests [FIT], guaiac fecal occult blood testing [gFOBT ] , and stool DNA [sDNA] testing) and direct visualization tests (colonoscopy, flexible sigmoidoscopy [FS]. and computed tomography colonography [CTC]).
| Reach, population and intended audience |
The goal is to guide clinicians on the age to start and stop screening and selection of the type and frequency of screening tests in average-risk asymptomatic adults.
Average CRC risk is defined as no prior diagnosis of CRC, adenomatous polyps, or inflammatory bowel disease, and no personal diagnosis or family history of known genetic disorders that predispose a person to a high lifetime risk of CRC (e.g. example, Lynch syndrome).
| Age to start screening |
The evidence identified no studies reporting results for initiating CRC screening only in adults younger than 50 years. People aged 60 years and older had greater reductions in CRC mortality compared to people younger than 60 years. One trial found a greater reduction in CRC mortality in people aged 65 to 74 years compared to those aged 55 to 64 years.
Starting screening at age 45 compared with age 50 resulted in more years of life gained and prevented a small number of CRC cases and deaths. However, there was also an increase in the number of colonoscopies and colonoscopy complications, such as cardiovascular and gastrointestinal events.
| Age to stop CRC screening |
The review identified no studies that enrolled or reported outcomes for CRC screening only in adults over 75 years of age.
Stopping screening at ages 80 and 85 years, compared with age 75 years, was found to prevent little or no additional incidence of CRC, but conferred an increase in colonoscopies and a slight increase in study complications.
| Screening test for CRC |
> Stool tests
• gFOBT
Efficacy : Five trials, with a follow-up range of 11 to 30 years, found that biennial gFOBT screening reduced CRC mortality at approximately 20 years and 30 years.
Damage : There is no known direct serious damage because gFOBT is non-invasive. The authors found harms of colonoscopy after an abnormal gFOBT result.
• FIT
Efficacy : Screening with biennial FIT was associated with lower CRC mortality compared with no screening.
Harms : Fecal immunochemical tests are non-invasive and no severe harms are known. The evidence review found harm in colonoscopy after an abnormal FIT result.
• DNA test
Efficacy : The evidence review found no studies evaluating sDNA testing and CRC incidence and mortality or all-cause mortality.
Harm : Stool DNA testing is non-invasive and no serious harm is known. The false positive rate of sDNA testing for CRC is higher than for gFOBT and FIT, which can lead to more colonoscopies, screening, and harm.
> Direct viewing tests
• Colonoscopy
Efficacy : It was associated with lower CRC mortality at 24 years of follow-up.
Damage : 3.1 perforations were reported per 10,000 procedures and 14.6 serious bleeding events were reported per 10,000 procedures.
• CTC
The authors did not identify eligible studies evaluating the effectiveness of CTC for CRC detection.
Damage : perforations were reported, all asymptomatic and in patients undergoing manual insufflation, as well as isolated serious hemorrhagic events.
• F.S.
Efficacy : Flexible sigmoidoscopy reduced CRC incidence and mortality.
Damage : The rate of serious bleeding events was 0.5 per 10,000 procedures. A colonoscopy after an abnormal FS resulted in 20.7 major bleeding events per 10,000 procedures.
| Screening test costs |
Screening more frequently than recommended is unlikely to provide significant additional benefit. However, it will increase false positive results, harm, and burden by using already limited healthcare resources.
Additional problems with cancer screening in general include overdiagnosis (a condition or disease that would not cause symptoms or death during a person’s lifetime) and associated overtreatment.
| Multiple chronic conditions |
Comorbidities reduce age-adjusted life expectancy and may influence the initiation, discontinuation, and frequency of CRC screening. Serious comorbidities include, but are not limited to, chronic obstructive pulmonary disease, diabetes, heart failure, moderate to severe liver disease, chronic hepatitis, advanced chronic kidney disease or end-stage renal disease, and dementia.
Due to the slow growth rate of most adenomas and, if they develop, subsequent CRC, the time needed to obtain a benefit from screening is long (10 years are needed to reduce 1 CRC death per every 1000 people examined). Study models suggest that any benefits from reducing mortality are outweighed by harms for patients with a life expectancy of less than 10 years, and possibly longer, due to age or comorbidities.
| Differences by biological sex |
Men have a higher risk of developing and dying from CRC than women, although the absolute differences are small (43.4 vs. 32.8 per 100,000 and 15.7 vs. 11.0 per 100,000, respectively).
| Evidence gaps and research need |
Future research should focus on studying the benefits and harms of screening in people younger than 50 years and older than 75 years to better understand optimal CRC screening intervals and starting and ending ages.
Ongoing comparative trials should better inform the selection and frequency within (e.g., colonoscopy every 10 to 15 years) and between (e.g., FIT versus sDNA) CRC screening tests.
