ACG issues updated colorectal cancer screening guidelines

March 9, 2021

The American College of Gastroenterology has issued updated evidence-based screening guidelines for colorectal cancer (CRC) in The American Journal of Gastroenterology, which recommend all average risk individuals begin screening at age 45. ACG has recommended that African Americans begin screening at age 45 since 2005.

The guidelines’ co-authors are Aasma Shaukat, MD, MPH, FACG; Charles J. Kahi, MD, MSc, FACG; Carol A. Burke, MD, FACG; Linda Rabeneck, MD, MPH, MACG; Bryan G. Sauer, MD, MSc, FACG (GRADE Methodologist); and Douglas K. Rex, MD, MACG. 

“One of the ACG’s primary objectives in updating its colorectal cancer screening guidelines is to update the 2009 guidelines in light of new evidence on age to initiate CRC screening, modalities, and interventions to improve screening rates,” said lead author Dr. Aasma Shaukat.   

There is a sense of urgency to the updated guidelines as colorectal cancer screening rates have declined during the COVID-19 pandemic and, even before the pandemic, obstacles to CRC screening meant that use of CRC tests was suboptimal. The authors wrote, “Despite the availability of multiple screening modalities and various public health initiatives to boost colorectal cancer screening, nearly one-third of the eligible United States population is unscreened. Colorectal cancer screening rates must be optimized to reach the aspirational target of >80%.”  

The authors point to recent studies highlighting a rising incidence of CRC in individuals younger than age 50 in the United States. While CRC incidence has shown continued decline in those 50 and older, the incidence rates have doubled in 20- to 49-year-olds. It has been estimated that persons born around 1990 have twice the risk of colon cancer and four times the risk of rectal cancer compared to those born around 1950. 

Dr. Shaukat outlined key recommendations in the new guidelines: 

  • Age to Initiate Screening - We suggest starting CRC screening at age 45 in average risk individuals and using either colonoscopy or fecal immunochemical test (FIT) as the primary screening modality. Other screening options include multitarget stool DNA test, CT colonography, and colon capsule. 
  • Family History of CRC - We recommend starting CRC screening at age 40 in individuals with one or two first degree relative with colorectal cancer or advanced colorectal polyps. If the first degree relative is <60, or there are two or more first degree relatives with colorectal cancer or advanced colorectal polyps at any age, colonoscopy should be used, and screening repeated at five-year intervals. If the first degree relative is age 60 or older, any screening modality can be used and, if normal, follow average risk screening intervals. For individuals with history of only one second degree relative with colorectal cancer or advanced polyps, we suggest using average risk recommendations. 
  • Aspirin - Aspirin is not a substitute for colorectal cancer screening and we suggest a narrow category of individuals that may use aspirin, in addition to routine screening, to reduce their risk of colorectal cancer: persons that are age 50- to 69 with cardiovascular disease risk of at least 10% and willing to take aspirin for at least 10 years.  
  • Quality Indicators - We recommend quality indicators for colonoscopy of Adenoma Detection Rates of at least 25%, withdrawal time of at least six minutes and cecal intubation rate of at least 95% for screening exams. 
  • Improving Adherence to Screening - We also provide evidence-based interventions to boost screening rates and suggest having an organized system of screening and follow up to reduce disparities and boost screening rates. 

An important clinical development is the distinction the new guidelines make between one-step screening tests and two-step screening tests. The authors wrote, “One approach to CRC screening tests is to divide them as one-step (direct) tests (i.e., colonoscopy which is diagnostic and therapeutic) or two-step tests that require colonoscopy, if positive, in order to complete the screening process. All of the screening tests other than colonoscopy are two-step tests. A major limitation of non-colonoscopy-based CRC screening tests (stool-based, flexible sigmoidoscopy, CT colonography or colon capsule) is that a positive test requires a follow-up colonoscopy. This two-step testing approach represents a continuum of screening, requires strong systems-based support to complete the screening cascade, and is more effectively applied in organized screening.” 

The authors described CRC’s disproportionate impact among African Americans, “African Americans have one of the highest rates of colorectal cancer of any racial/ethnic group in the United States. Compared to whites, incidence rates are 24% higher in African American men and 19% higher in African American women. Stage adjusted CRC mortality is also disproportionately higher in African Americans, with rates being 47% higher in African American men and 34% higher in African American women compared to whites. The reasons for these differences are not entirely clear but disparities in care, such as lower rates of screening, diagnostic follow up, and treatment are postulated.” They add, “Based on recent SEER data, modelling studies show similar benefit of CRC screening in African Americans and whites starting at age 45. Special efforts and outreach programs are needed to boost screening among African Americans, in order to reduce the disparities in screening rates and reduce incidence rates.” 

The full text of the guideline is posted on the AJG site at