What Are Colorectal Cancer Risk Factors, and Who Is at Risk?
What is Colorectal Cancer?
Colorectal cancer occurs when cells in the colon (large intestine) or rectum (the end of the large intestine that connects to the anus) grow abnormally. Most colorectal cancers start as a polyp or polyps (small growths that form in the lining of the intestine) that change over time. About 95% of colorectal cancers stem from acquired mutations, not inherited conditions. Acquired mutations do not pass from parent to child.
What Groups Are at Greater Risk for Colorectal Cancer?
- While colorectal cancer rates are rising for people younger than 50, it more commonly develops after age 50.
- Men have a slightly higher risk than women.
- The Black community suffers the highest colorectal cancer rates in the United States. They are 20% more likely to get this form of cancer and about 40% more likely to die than other racial or ethnic groups in the U.S. Black women have a higher mortality rate than women from any other group, and Black men are more likely than Black women to die from this disease.
- Ashkenazi Jews (Jews of Eastern European descent) have one of the highest risk rates of any ethnic group worldwide.
- Individuals with inherited syndromes linked to colorectal cancer, such as Lynch syndrome (HNPCC) and familial adenomatous polyposis (FAP), are at higher risk. While rare, these cases still make up about 5% of colorectal cancers. Genetic testing can determine whether family members are carriers of these gene mutations, enabling earlier intervention and medical management to help reduce risk.
- Anyone with a history of adenomas (a type of polyp that can change over time) is at increased risk – especially if the adenomas were large, multiple in number, or showed signs of dysplasia (having abnormal, pre-cancerous cells). Adenomas can be tubular, villous (frondlike), or a combination of both, tubulovillous.
- Those with a history of colorectal cancer are more likely to develop new cancers in other parts of the colon or rectum, especially those first diagnosed at a younger age (under 50). Former ovarian or uterine cancer patients are also at increased risk.
- Individuals with inflammatory bowel disease (IBD), such as ulcerative colitis or Crohn’s disease, are more likely to develop colorectal cancer due to the long-term effects of inflammation.
- Persons with type 2 diabetes are associated with higher risk.
What Other Colorectal Cancer Risk Factors Are There?
Various external factors are also linked to an increased risk of colorectal cancer:
- Being overweight or obese. Extra weight can raise insulin, insulin growth factor, and estrogen hormones. Excessive levels of these hormones can increase the chance that certain cancers will develop. Additionally, low-level inflammation is more common in people who are obese, which can create an environment conducive to cancer.
- Physical inactivity or a highly sedentary lifestyle
- Low levels of vitamin D
- High consumption of processed or red meats
- Meats cooked at high temperatures (fried, grilled, barbecued, or broiled) create HCAs and PAHs — chemicals that may cause DNA mutations that can cause cancer
- Smoking and moderate to heavy alcohol use
What Steps Can Be Taken to Reduce Risk?
The American Cancer Society guidelines provide recommendations for maintaining a healthy weight, lifestyle, and diet, all of which can reduce cancer risk:
- Adults should set weekly goals for 150 – 300 minutes of moderate-level exercise or 75-150 minutes of intense physical activity.
- Reduce or limit sedentary behaviors where possible. Make movement a daily habit and take breaks from prolonged sitting and screen time.
- Incorporate fiber and nutrient-rich fruits, vegetables, and whole grains into your diet.
- Curb consumption of processed meats and foods, sugar-sweetened drinks, and refined grains.
When Are Screening Tests Appropriate?
The American Cancer Society recommends screening at age 45 or sooner if a family history of colorectal cancer is identified.
The most common colorectal cancer symptoms can include the following:
- Any change in bowel habits that lasts for more than a few days. Changes include diarrhea, constipation, or pencil-thin stools
- The sensation of pressure that makes a person feel like they need to have a bowel movement even after having one
- Abdominal cramping or pain
- Rectal bleeding or blood in the stool which may make the stool look dark brown or black
- Feeling fatigued or weak; losing weight without consciously trying
Many of these symptoms can be associated with other non-cancerous conditions, such as hemorrhoids, irritable bowel syndrome (IBS), or other infections. However, any irregularities should be discussed with and monitored by a doctor. Proper diagnoses and treatment plans are essential for maintaining good health.
“Symptoms affiliated with colorectal cancer are not exclusive to the disease. Still, it is important to get checked out if any ailment persists. Always seek a medical opinion whenever there are health concerns, especially where a family history of colorectal cancer exists, and maintain a regular screening schedule,” notes Dr. Brittany Case, medical oncologist at Southern Cancer Center. “Regular screening can help us monitor your health and detect changes we want to stay in front of.”