A New Playing Field: ACG's Latest Guidelines Move the Goalposts for CRC Screening

David A. Johnson, MD


March 30, 2021

This transcript has been edited for clarity.

Hello. I'm Dr David Johnson, professor of medicine and chief of gastroenterology at Eastern Virginia Medical School in Norfolk, Virginia.

The American College of Gastroenterology (ACG) just released their 2021 clinical guidelines for colorectal cancer screening. To develop their evidence-based recommendations, the authors identified several key questions and then surveyed the latest evidence on the topic. I wanted to give you some highlights from their work in order to guide your clinical judgment and care.

It is estimated that in 2020 in the United States there were approximately 148,000 new cases of colorectal cancer and 53,000 deaths resulting from this disease; this shows that there is clearly room for improvement. Approximately 70% of colorectal cancer develops from the traditional adenoma carcinoma sequence, whereas 30% develops from the sessile serrated lesion-to-carcinoma pathway, a new form of categorization that replaces the term "sessile serrated polyps."

One-Step or Two-Step Approaches

The authors begin their recommendations by defining one- or two-step approaches to screening for colorectal cancer.

A one-step approach, obviously, calls for colonoscopy with diagnosis and therapeutic polypectomy performed at the same time.

The two-step approach encompasses all other types of screening besides colonoscopy. This also includes capsule colonoscopy, which is not covered for screening in the United States but is covered for patients with previously incomplete colonoscopy or lower gastrointestinal bleeding. Central to all the two-step approaches is the recognition that a positive test should be followed by a confirmatory colonoscopy. That needs to be discussed and made clear to patients who may be reluctant to undergo colonoscopy.

There are other recommendations of importance relating to stool DNA testing, including fecal immunochemical testing (FIT). The authors state that when these tests are positive, and a high-quality follow-up colonoscopy is performed with adequate preparation, those patients could then return to a normal screening interval based on their preferred strategy going forward. Although some early literature suggested that these patients required closer follow-up, that has not been proven in subsequent studies and is therefore not included in the ACG's latest recommendations.

Updated Age Thresholds for Screening

Of note is the ACG's recommendation to begin screening in average-risk individuals at 45 years of age. This is because although colorectal cancer incidence is decreasing in those 50 years of age and older, it is increasing substantially among those 20-49 years of age. There is also evidence that those born around 1990 have twice the risk for colon cancer and four times the risk for rectal cancer than those born around 1950.

The recommendation to begin screening at 45 years is considered conditional and based on low-quality evidence. Conversely, the recommendation to screen in average-risk individuals between 50 and 75 years of age is considered strong and based on moderate-quality evidence.

When patients are older than 75 years of age, this marks the time to begin discussing with them whether or not they need continued screening. There is potentially a decreased value in screening elderly patients. The beneficial effect of neoplastic polyps lags for cancer prevention for maybe 7-10 years, and there are incremental risks for other associated causes of death. Therefore, this decision needs to be made on an individualized basis, which is also consistent with the latest guidelines from the US Preventive Services Task Force in individuals aged 76-85 years old. In patients aged 86 years and older, screening is not recommended.

You may recall that the ACG previously recommended to begin screening African Americans at age 45, which has since been extended to all patients in that age group. However, we must continue to recognize that African Americans tend to have an earlier onset of colorectal cancer and more advanced stage at presentation. If screening is negative, then African American patients can go into a 10-year standardized interval.

Regarding family history, the ACG suggests beginning screening with colonoscopy at age 40 in those with any first-degree relative < 60 years old with colorectal cancer or advanced adenoma, or two first-degree relatives at any age. This should be followed by colonoscopy at 5-year intervals.

The ACG's guidelines here also identify screening recommendations for familial risk of sessile serrated lesions. They advise that lesions of this type considered high risk (≥ 10 mm, including dysplasia of any size or the traditional serrated adenoma) would qualify as an advanced adenoma, with screening again beginning at age 40 or 10 years before the index case.

If the individual has a first-degree relative ≥ 60 years of age with colorectal cancer or advanced polyp, they should also have an initiation point for screening at 40 years old and then be enrolled in a 10-year screening protocol based on average risk going forward, with the recognition that risk goes down as the individual becomes older.

Additional Takeaways of Interest

The guidelines also provide a couple of points worth highlighting regarding performance characteristics.

Adenoma detection rate remains the cardinal concern here. There was some question about including adenoma detection rate across a number of indications for screening, surveillance, colonoscopy, and diagnostic colonoscopy. The authors address this by recognizing that for serial surveillance, the adenoma detection rate goes up to approximately 7%-10% higher than screening comparisons, with detection rates lower with diagnostic colonoscopy. Also, the FIT-positive population has a higher threshold for the adenoma detection rate, which should be 45% for males and 35% for females.

The authors include additional information for adenoma detection in sequential average-risk screening colonoscopies. Previously, as you may recall, the adenoma detection rate was obtained at index exam. Now it is recommended that all screening for an average-risk individual should be included in that composite number.

Finally, the authors provided recommendations pertaining to aspirin use. The authors suggest the use of low-dose aspirin in patients with ≥ 10% risk of developing cardiovascular disease over the next 10 years. Studies have shown that the sustained use of aspirin was associated with a 40% decreased incidence of colorectal cancer and a decrease in colon cancer–related deaths at 20 years. Although bleeding considerations may require withholding aspirin, it does seem to be associated with relative risk reduction for both cancer and colorectal cancer–related death.

The ACG always provides us with valuable clinical perspective to guide our decisions. Hopefully, this 30,000-foot view of their latest screening guidelines in colorectal cancer will be of value to you.

I'm Dr David Johnson. Thanks again for listening.

David A. Johnson, MD, a regular contributor to Medscape, is professor of medicine and chief of gastroenterology at Eastern Virginia Medical School in Norfolk, Virginia, and a past president of the American College of Gastroenterology. His primary focus is the clinical practice of gastroenterology. He has published extensively in the internal medicine/gastroenterology literature, with principal research interests in esophageal and colon disease, and more recently in sleep and microbiome effects on gastrointestinal health and disease.

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