Colorectal cancer risk factors

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To view the risk factors of familial adenomatous polyposis (FAP), click here
To view the risk factors of hereditary nonpolyposis colorectal cancer (HNPCC), click here

Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1] Associate Editor(s)-in-Chief: Saarah T. Alkhairy, M.D.


There are both genetic and environmental factors that can increase the risk of colorectal carcinoma (CRC). Some of the genetic risk factors are familial adenomatous polyposis and hereditary non-polyposis colorectal cancer. Some environmental risk factors are personal/family history, history of inflammatory bowel disease, diet, alcohol, cigarette smoking, race, and gender.

Colorectal Cancer Risk Factors

The causes and the risk factors for colorectal carcinoma are the similar. There are both genetic and environmental factors that can increase the risk of colorectal carcinoma.[1] FAP and HNPCC are the most common risk factors of CRC, but together these two conditions account for only about 5 percent of CRC.[2]

Genetic Risk Factors

The table below lists the genetic risk factors for colorectal carcinoma:[3][4]

Genetic Risk Factor Description
Familial Adenomatous Polyposis (FAP)
  • Autosomal dominant inheritance
  • Other variants include Gardner's syndrome, Turcot's syndrome, and attenuated adenomatous polyposis coli
  • Caused by germlines mutations in the APC gene
  • Colonic cancer occurs in 90% of untreated individuals around 45 years

To view Gardner's syndrome, Turcot's syndrome, and attenuated adenomatous polyposis coli , click here

MUTYH-associated Polyposis (MAP)
Lynch Syndrome AKA Hereditary Non-polyposis Colorectal Cancer (HNPCC)
  • Autosomal dominant inheritance
  • Caused by a defect in one of the mismatch repair genes, most commonly hMLH1, hMSH2, hMSH6, or PMS2
  • Mean age at initial cancer diagnosis is around 48 years

Environmental Risk Factors

The table below lists the environmental risk factors for colorectal carcinoma:[5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20][21][22][23]

Environmental Risk Factor Description
Family History Risk increases with number of family members affected and the age of diagnosis
  • If there is a single affected first-degree relative with CRC; the risk further increases if two first-degree relatives have CRC diagnosis
  • If age of diagnosis is less than 50-60 years, the risk significantly increases especially if the family member has an adenomatous colonic polyp
Personal History Risk increases if there is a personal history of CRC or adenomatous polyps, particularly:
Ulcerative Colitis The increase in risk begins about 8 to 10 years after the initial diagnosis of pancolitis and at 15 to 20 years
Crohn's Disease There is an increased risk:
  • If 1/3rd or more of the colonic mucosa is involved
Age The risk of developing CRC increases with age;
  • Majority of cases occur in the 60s and 70s, while cases before age 50 are uncommon unless a family history of early colon cancer is present
  • Cancer in African American individuals tends to occur earlier
Abdominal Radiation
  • Adult survivors of childhood malignancy who received abdominal radiation are at significant risk
Race The African American race has the highest CRC race of all the ethnic groups
  • The mortality is 20% higher in the African American race compared to the Caucasian race
  • CRC mortality is about 20-40 percent higher in men than in women
Diabetes Mellitus and Insulin Resistance Although it is not clear why but one possible explanation linking diabetes to CRC is hyperinsulinemia
  • Insulin is an important growth factor for colonic mucosal cells and stimulates colonic tumor cells
  • The elevated risk may be related to interference of folate absorption by alcohol and decreased folate intake
Obesity Every 5 kg/m2 increase in BMI was associated with:
  • Twenty four percent increased incidence of both colon and rectal cancer in men
  • Nine percent higher incidence of colon cancer in women
Cigarette Smoking Risk of developing CRC was increased among cigarette smokers compared to those who never smoked;
Uretercolic Anastomoses
  • There is increased risk of neoplasia in close proximity to the ureteric stoma
Diet Diets associated with an increased risk of CRC include:
  • Long-term consumption of red meat or processed meats
  • Diets low in vegetables and high in fats
Coronary Heart Disease
Sedentary Lifestyle
  • Regular exercise stimulates peristalsis, thereby decreasing transit time for carcinogenic substances in the colon
Other cancers The following cancers have been associated with an CRC especially if the first diagnosis was made at an early age:


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