This article delves into the updated colorectal cancer (CRC) screening guidelines from the American College of Physicians (ACP). It discusses factors influencing CRC risk, emphasising the importance of understanding metabolic pressures, genetic factors and lifestyle risks. 

The American College of Physicians (ACP) issued an update on August 1 to their guidance for colorectal cancer (CRC) screening in asymptomatic average-risk adults. Published in the Annals of Internal Medicine, the guidance suggests that healthcare providers start screening patients at age 50 if they are asymptomatic and at average risk.[1][2]

"The net benefit of colorectal cancer screening is much less favourable in average-risk adults between ages 45 to 49 years than 50 to 75 years. Although there has been a small increase in CRC incidence among individuals aged 45 to 49 years, the incidence is much lower than in individuals aged 50 to 64 years and 65 to 74 years," stated the study.

According to the ACP’s release, the updated guidance statement was “developed using recently published and critically appraised clinical guidance from national guideline developers since the publication of the American College of Physicians’ 2019 guidance statement,” in addition to guidance from other countries released between January 2018 and April 2023.[1]

Guidance statements established by the ACP

1. Healthcare providers should start screening for CRC in asymptomatic average-risk adults at age 50. 
2. Healthcare providers should consider not screening this same patient group between the ages of 45 and 49, considering the uncertainty around the benefits and harms of screening in this population.
3. Healthcare providers should stop CRC screening in asymptomatic average-risk adults over 75 or in asymptomatic average-risk adults with a life expectancy of 10 years or less. 
4. Healthcare providers should work with their patients to select a CRC screening test that takes into account “benefits, harms, costs, availability, frequency, and patient values and preferences.”
5. CRC screening options should include a faecal immunochemical or high-sensitivity guaiac faecal occult blood test every two years, a colonoscopy every 10 years, or a flexible sigmoidoscopy every 10 years, and a faecal immunochemical test every two years. For patients between the ages of 50 and 60 who prefer less frequent screenings, a colonoscopy every 15 years may be reasonable. 
6. To screen for CRC, healthcare providers should not use “stool DNA, computed tomography colonography, capsule endoscopy, urine, or serum screening tests.”

According to an accompanying editorial published by the Annals of Internal Medicine, the ACP’s new guidance is based on data from the United States. Preventive Services Task Force (USPSTF) and American Cancer Society.

The authors say that, when formulating its recommendations, the ACP “emphasized the importance of clinical and empirical data in the context of absolute disease prevalence, rather than relying solely on disease modelling.” Additionally, they say that the ACP considered patient costs.

“The ACP panel also paid attention to the risks and burden for patients and societal issues, such as equality, with the different screening tests.”

The authors also say that they stand behind the ACP’s suggestion that asymptomatic average-risk individuals under 50 should not be screened for CRC: “The reasoning includes a lack of evidence on clinically relevant absolute benefits as compared with the expected harms of screening in this age group. It may seem intuitive to expect similar relative screening benefits and harms for younger people compared with older people.

However, considering the much lower disease risk, a much larger number of younger people will need to be screened to prevent 1 case of cancer. Consequently, ACP cautions that absolute screening benefits may not outweigh the harms in this age group. We agree.”

What do healthcare providers think?

Regarding the guidance that recommends against using stool DNA, computed tomography colonography, capsule endoscopy, urine, or serum screening tests for CRC, Dr. Anton Bilchik, MD, PhD, Surgical Oncologist, Chief of Medicine, and Director of the Gastrointestinal and Hepatobiliary Program at Saint John’s Cancer Institute in Santa Monica, CA, says that “These tests are expensive and can lead to unnecessary colonoscopies because they have a higher rate of false positive results.”

Dr. Bilchik also says that the recommendation regarding screening test selection is a “more cost-effective, convenient approach to early detection of colon cancer. It also reduces the need for more frequent colonoscopies.”

A closer look at colorectal cancer

Screening for CRC is essential; in the US, CRC has the fourth highest cancer incidence and ranks second in mortality among cancers. Between 2000 and 2019, CRC affected patients under 50 at a higher rate, increasing from 6 to 8.7 per 100,000 people. And more younger people are dying from the disease.[4] 

According to a study published in Cancer Control, urbanisation and Western lifestyle risks, including obesity, physical inactivity, smoking, and high salt and red meat consumption, may contribute to increased CRC risk. Obesity, in particular, is associated with CRC in younger adults, according to a 20-year study published in the Journal of Gastrointestinal Oncology.[5]

Dr. Joel Levine, MD, Co-director and Founding Director of the Colon Cancer Prevention Program at UConn Health’s Carole and Ray Neag Comprehensive Cancer Center, says that “it is critical to understand that metabolic pressures are key to risk. Obesity and related metabolic changes have a significant impact on cell biology and inflammation signalling. We now know that the colon microbiome is a main contributor to homeostasis and dysbiosis of varied types and is known to contribute to the origins and progression of diverse polyp pathways (adenoma serrated lesions ).”

Regarding risk, Dr. Levine adds,

“The ‘risk’ for colon cancer is important to define. First, family history. Although only a few percent have identifiable inherited deleterious genes.” “But when there is a first-degree relative with CRC, data suggests that about 30% of such families have a ‘genetic’ element contributing to the risk,” he says.

Other risk factors include night shift work, insufficient vitamin D, a history of inflammatory bowel disease, colorectal or adenomatous polyps, or type 2 diabetes.[6]  

Additionally, the ACP notes that rates of CRC vary by sex, race, and ethnicity. Males and non-Hispanic American Indian or Alaska Native persons and non-Hispanic Black persons experience the highest rates of CRC.

However, the ACP notes in its guidance statement that “absolute differences between biological sex and racial and ethnic groups are small.” Jewish people of Eastern European descent (Ashkenazi Jews) are also at high risk.[7] 

In the end, Dr. Levine notes, “One has to be very careful about the term, ‘average risk’ when considering colon cancer screening and surveillance. Guidance is helpful, but [healthcare providers should] look at large outcome trials comparing one method of screening versus another.”

Disclaimer: This story is contributed by Lisa Marie Basile and is a part of our Global Content Initiative, where we feature selected stories from our Global network which we believe would be most useful and informative to our doctor members.