For a long while I’ve wondered if growing up in the 80s in my suburban town north of Boston came with a higher risk of colorectal cancer. It started as a joke about living near a waste management plant. Then my older sibling had a friend who had colon cancer in his early 40s. And then another. And a third. All under the age of 50. No longer a laughing matter, these events made me wonder if there was a shift in the incidence of colorectal cancer in people younger than age 50. Around this same time (2018), the American Cancer Society (ACS) updated their guidelines for colon cancer screening from starting at age 50 (for low/average risk) to age 45. The US Preventative Services Task Force (USPSTF) subsequently modified their guidelines in 2021 to reflect this earlier screening age as well. So – why? Why did they lower the age for initial screening? Turns out – it's fairly complicated.
Just this week, the British Journal of Surgery released their review on the causes of early-onset gastrointestinal (GI) cancers. They note that the incidence of GI cancers is rising globally at alarmingly high rates. Some modifiable causes for this include obesity (having a BMI ≥ 30kg/m2), having a Western diet (high calorie, low nutrient and processed foods), sedentary lifestyle, excessive alcohol consumption, smoking, and metabolic dysfunction-associated steatotic liver disease (MASLD) (formerly known as non-alcoholic fatty liver disease). Additionally, there’s an increasing likelihood that microplastics are responsible for this increasing rate. Their direct cause on our GI system is not entirely clear, but many experts believe that microplastics are negatively affecting our gut microbiota and/or damaging the barrier integrity of the colonic mucus layer, thus reducing its protective effect.
Another interesting study released this week in Nature Medicine describes the impact of undiagnosed and untreated H.pylori GI infections worldwide. Their data suggest that 75% of the 15.6 million expected cases of gastric cancer would be prevented if H.pylori infection is eradicated. There has been no causal relationship noted between H.pylori and colorectal cancer; however, experts acknowledge that there needs to be more research into whether there are indirect effects of H.pylori on the GI system by modifying the gut microbiome or causing chronic inflammation.
While the cause(s) of these increasing rates of early-onset colorectal cancer may not be entirely clear, there is no dispute over the data. Help your patients by reviewing the colorectal screening guidelines published by the ACS and USPSTF and arm yourself with rationale for them as to why they should get their colon cancer screening earlier than they may have thought.
American Cancer Society: https://www.cancer.org/health-care-professionals/american-cancer-society-prevention-early-detection-guidelines/colorectal-cancer-screening-guidelines.html
US Preventative Services Task Force: https://www.uspreventiveservicestaskforce.org/uspstf/recommendation/colorectal-cancer-screening