Approximately 4.3% of people will be diagnosed with colon cancer during their lifetimes. There are many different causes and risk factors for developing colon cancer, including genetics, environment, and chance. As with most cancers, a specific cause for the great majority of colon cancers cannot be identified. Rather it is likely that there are multiple factors which play a part in the development of the cancer. The good news is that screening for colon cancer is highly effective in reducing the frequency and severity of colon cancer, both in the general population as well as for persons with a hereditary risk.    

Some of the factors that are known to increase the risk for colon cancer are:

Demographics

• Age: the risk for colon cancer (and most other cancers) increases as we get older.
• Race: data has shown that African Americans have increased risk to develop colon cancer, as well as increased incidence of deaths from colon cancer.  The reasons for these differences are not fully understood, but may in part be due to differences in access to screening for colon cancer.

Lifestyle/Environmental Factors

• Alcohol consumption: three or more drinks of alcohol per day has been associated with elevated risk for colon cancer.
• Cigarette smoking: smoking has been implicated as a risk factor for multiple different cancers, including colon cancer.
• Obesity

Personal Medical Factors

• Previous history of colon polyps: a history of colon polyps, specifically adenomatous polyps or sessile serrated polyps, indicates increased risk for future polyps and/or cancer if the polyps are not sufficiently managed.
• Previous history of colon cancer: individuals with a history of colon cancer are at increased risk not only for recurrence of that cancer, but for development of a second cancer.
• Inflammatory bowel disease (ulcerative colitis, Crohn’s disease): chronic inflammation of the colon tissues can damage the cells and, over time, can lead to cancerous changes in the colon tissue.

Family History

• Family history of colon cancer or advanced adenomatous polyps: how high the risk is depends on how many relatives have been diagnosed, how closely you are related to the family members who have been diagnosed, and how old those relatives were when they were diagnosed.
• Hereditary cancer syndromes: approximately 5-10% of colon cancers are due to inherited genetic mutations which increase the risk for colon cancer.  Several different genes and genetic syndromes are known to be associated with increased risk for colon cancer.  The links below provide more information about hereditary colon cancer genes.

Genes related to an increased risk for colon cancer (click on them for more information):

• Lynch syndrome (MLH1, MSH2, PMS2, MSH6, and EPCAM)
• Familial Adenomatous Polyposis (APC)
• AXIN2-related Colon Cancer
• CHEK2-related Colon Cancer
• GREM1-related Colon Cancer
• Juvenile Polyposis syndrome (BMPR1A, SMAD4)
• MSH3-related Colon Cancer
• MUTYH-Associated Polyposis
• NTHL1-related Colon Cancer
• POLD1-related Colon Cancer
• POLE-related Colon Cancer
• PTEN Hamartoma Tumor syndrome (PTEN)/Cowden syndrome
• Serrated Polyposis syndrome
• Peutz-Jeghers syndrome (STK11)
• Li Fraumeni syndrome (TP53)

Click here to learn more about scheduling a genetic counseling appointment for questions about hereditary cancer predisposition.

Additional Resources

*Positive Results Facebook Group
Genetic Support Foundation hosts a Facebook group for Hereditary Cancer Support and Resources. Get trusted information and join a community of support.
*Cascade Screening Connector
Genetic Support Foundation has partnered with the Washington State Department of Health to provide cascade screening to help people identify and contact family members who may have an increased chance of developing cancer. 
*FORCE (Facing Our Risk of Cancer Empowered) 
The FORCE mission is to improve the lives of individuals and families facing hereditary cancer. Resources include peer navigation and expert-reviewed information. 
*AliveAndKicknAliveAndKickn is a nonprofit working to improve the lives of individuals and families affected by Lynch Syndrome and associated cancers through research, education, and screening. 
*Health Experiences USAThis national research project brings patient voices into the healthcare experience and features video clips of people facing hereditary cancer. Individuals from a variety of backgrounds share both positive and negative experiences about living with hereditary cancer. 

---