New Colorectal Cancer Screening Guidelines


Colorectal cancer is one of the three most common cancers in the United States along with lung cancer and breast/prostate cancer for women and men, respectively.  As a result, effective screening methods for colorectal cancer have been developed.

Usually screening for colorectal cancer is performed with a colonoscopy, that examines the entire large bowel, or a sigmoidoscopy, which goes up to the left side of the colon.  According to previous guidelines screening for colorectal cancer was set at the age of 50 and repeating colonoscopy every 10 years. Recently, however, this recommendation has been changed, such that average risk individuals are to start screening at the age of 45.  The change has been made by the American Cancer Society (ACS) in their latest guidelines published in 2018 based on the study that ran for about a decade, from about 1994 to 2014.

A concerning trend with a 50% increase in colorectal cancer was observed in this study, particularly in those under 50 years of age, with a predilection for right-sided colon cancers.  As a result, ACS updated their original guidelines, and recommended starting screening for colorectal cancer 5 years earlier. The rational of earlier screening is to be more proactive about early detection.  Indeed, for many cancers, early detection means higher chances of successful treatment outcomes and potentially improved survival.  

1 in 2 people in the US will be Diagnosed with an Invasive Cancer During their Lifetime.

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An obvious question is why are colorectal cancer rates rising so drastically in younger individuals and what can be done about this concerning trend?

Research suggests that more that 85% of cancer is closely linked to our lifestyle, diet and exposures.  A study conducted by the University of Pittsburgh and Imperial College London and published in Nature Communications found a marked correlation between our diet and the health of our gut. The study included two groups of people: 20 African Americans and 20 people from rural South Africa. The African American group had a typical Western diet, rich in processed food, low in fibers and high in fat.  The South African group’s diet consisted mainly of unprocessed fibers, carbs, and low in fat.

Before the study began, the participants' gut health was assessed, obtaining their microbiome signature (the types of bacteria residing in the gut, along with inflammatory markers).  The researchers found a significantly higher rates of polyps, inflammatory gut markers and "unhealthy, pre-cancerous" microbiome in the African American group as compared to the South African one.  Remarkably, after just a 2 week dietary switch – such that now the African Americans were put on the South African diet, and the South Africans on a typical Western one – the pre-cancerous microbiome and inflammatory marker signature reversed!  Just after 2 weeks of a diet rich in unprocessed carbs and fiber, the consumers of our "unhealthy" Western diet internally started looking more like their whole-food consuming counterparts! 

While starting to screen at the age of 45 can help with early detection it certainly does not address the underlying issue of lifestyle and dietary habits that have become a norm in our Western society.  Such diets of affluence intricately linked with the variety health issues, cancer being one of the common ones.   In sum, genetic predisposition can certainly lead to an early development of the colorectal cancer, what we do and eat indeed, play a key role in promoting carcinogens that contribute to colorectal and other cancers. 

--Additional Sources--

Begin Colorectal Cancer Screening at Age 45, Says ACS

Diet swap has dramatic effects on colon cancer risk for Americans and Africans -- ScienceDaily

Gut Microbes Combine to Cause Colon Cancer, Study Suggests - The New York Times

Colonization with enterotoxigenic Bacteroides fragilis is associated with early-stage colorectal neoplasia

Tumours grow where two gut bacteria thrive : Research Highlights