From the Guidelines
Colorectal cancer risk factors include a combination of non-modifiable and modifiable factors, with age, family history, and lifestyle choices such as diet and physical activity playing significant roles, as highlighted in the 2021 US Preventive Services Task Force recommendation statement 1. The non-modifiable risk factors for colorectal cancer include:
- Age, especially over 45 years, with nearly 94% of new cases occurring in adults 45 years or older 1
- Personal or family history of colorectal cancer or polyps
- Inflammatory bowel disease, such as Crohn's disease or ulcerative colitis
- Certain genetic syndromes, like Lynch syndrome or familial adenomatous polyposis
- Racial background, with higher risk in African Americans, American Indians, and Alaska Natives 1 Modifiable risk factors include:
- Lifestyle choices, such as a diet high in red and processed meats, low-fiber diet, obesity, physical inactivity, smoking, and heavy alcohol consumption, which can promote inflammation, alter gut microbiota, and cause DNA damage in colon cells 1
- Diabetes and insulin resistance, which also increase the risk of colorectal cancer Understanding these risk factors is crucial, as many colorectal cancers can be prevented through lifestyle modifications and regular screening, which should begin at age 45 for average-risk individuals or earlier for those with additional risk factors, as recommended by the US Preventive Services Task Force 1. Key points to consider in assessing risk include:
- The importance of age as a risk factor, with incidence rates increasing with age 1
- The higher rates of colorectal cancer incidence in certain racial groups, such as Black adults and American Indian and Alaskan Native adults 1
- The role of family history and other risk factors, such as obesity, diabetes, long-term smoking, and unhealthy alcohol use, in increasing the risk of colorectal cancer 1
From the Research
Risk Factors for Colorectal Cancer
The risk factors for colorectal cancer include:
- A personal or family history of advanced adenomas or colorectal cancer 2
- A personal history of inflammatory bowel disease, such as ulcerative colitis or Crohn disease with colonic involvement 2
- Genetic polyposis syndromes, such as hereditary nonpolyposis colorectal cancer, adenomatous polyposis syndromes, or Peutz-Jeghers syndrome 2
- A first-degree relative with colorectal cancer or advanced adenoma diagnosed before 60 years of age, or two first-degree relatives diagnosed at any age 2
Screening Recommendations for High-Risk Individuals
High-risk individuals should undergo more frequent or earlier testing than individuals at average risk, with screening recommendations including:
- Starting screening colonoscopy at 40 years of age or 10 years younger than the earliest diagnosis in their family, whichever comes first, for individuals with a first-degree relative with colorectal cancer or advanced adenoma 2
- Starting colonoscopy at 25 years of age and repeating every one to two years for individuals with a first-degree relative with hereditary nonpolyposis colorectal cancer 2
- Starting screening at 10 years of age or in a person's mid-20s, depending on the syndrome, and repeating colonoscopy every one to two years for individuals with a family history of adenomatous polyposis syndromes 2
- Starting screening colonoscopy at eight years of age in individuals with Peutz-Jeghers syndrome, with repeat colonoscopy at 18 years of age and then every three years if results are normal 2
General Screening Recommendations
General screening recommendations for average-risk individuals include:
- Starting colorectal cancer screening at 45 years of age and undergoing regular screening until 75 years of age 3, 4, 5
- Using one of several screening strategies, including high-sensitivity guaiac fecal occult blood test, fecal immunochemical test, multi-target stool DNA test, computed tomographic colonography, flexible sigmoidoscopy, or traditional colonoscopy 5