Colorectal Cancer: Risk Factors

The American Cancer Society estimates that there are roughly 97,000 new cases of colon cancer cases, and 40,000 new cases of rectal cancer in the United States each year.
A person’s lifetime risk of developing colorectal cancer is about 1 in 20 (5 percent). This risk is slightly lower in women than in men.

Colorectal cancer is the second leading cause of cancer related deaths for men and women (when both sexes are combined).

African Americans have a higher rate of colorectal cancer than whites, while Jews of Eastern European descent (Ashkenazi Jews) have some of the highest colorectal cancer risks of any ethnic group in the world, due to gene mutations.

Other risk factors include:

Age: Nearly 9 out of 10 people diagnosed with colorectal cancer are aged 50 or older.

Personal history of colorectal polyps or colorectal cancer: This is especially true if the polyps are large or there are many of them.

Personal history of inflammatory bowel disease: Inflammatory bowel disease (IBD), (including ulcerative colitis and Crohn's disease) causes long-term inflammation of the colon. People with IBD should be screened for colorectal cancer at an earlier age, and more often.

Family history of colorectal cancer or adenomatous polyps: While most colorectal cancers occur in people without a family history of colorectal cancer, about one in five patients have other family members affected with this disease. Having family members who have had adenomatous polyps is also linked to a higher risk. (Adenomatous polyps are the type that often become cancerous.)

Inherited syndromes: About 5 to 10 percent of people who develop colorectal cancer have inherited gene defects (mutations), the most common of which are familial adenomatous polyposis (FAP) and hereditary non-polyposis colorectal cancer (HNPCC). People with these genetic syndromes may develop colon cancer earlier in life and are at risk for other types of cancer. For instance, people with HNPCC are also at risk for uterine cancers if they are women. If diagnosed with colon cancer at a young age and/or several family members also have colon cancer or associated cancers, referral tfor cancer genetics risk assessment and counseling should be considered.

Other rare inherited conditions that increase risk include:

  • Turcot syndrome
  • Peutz-Jeghers syndrome
  • MUTYH-associated polyposis

Type II Diabetes: People with type II or non-insulin dependent diabetes have an increased risk of developing colorectal cancer and a less favorable outlook after diagnosis.
Diet: A diet that favors red meats and processed meats (hot dogs and some luncheon meats) increases colorectal cancer risk. A diet high in vegetables, fruits, and whole grains is recommended to lower risk.

Physical inactivity: A sedentary lifestyle may lead to a greater chance of developing colorectal cancer. Increasing activity may help reduce that risk.

Obesity: Extreme overweight increases risk of developing and dying from colorectal cancer. This is especially true for men.

Smoking: Long-term smokers are also more likely to develop and die from colorectal cancer.

Excessive alcohol consumption: To avoid the risk of developing colorectal cancer, alcohol use should be limited to no more than two drinks a day for men and one drink a day for women.