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Colon Cancer

What Causes Colon Cancer?

Last modified: 
20/03/2012 - 18:37

Contributing Author: Guy Slowik FRCS

There are several causes for colorectal cancer as well as factors that place certain individuals at increased risk for the disease. There are known genetic and environmental factors.

People at risk for colorectal cancer:

  • The biggest risk factor is age. Colon cancer is rare in those under 40 years. The rate of colorectal cancer detection begins to increase after age 40. Most colorectal cancer is diagnosed in those over 60 years.
  • Have a mother, father, sister, or brother who developed colorectal cancer or polyps. When more than one family member has had colorectal cancer, the risk to other members may be three-to-four times higher of developing the disease. This higher risk may be due to an inherited gene.
  • Have history of benign growths, such as polyps, that have been surgically removed.
  • Have a prior history of colon or rectal cancer.
  • Have disease or condition linked with increased risk.
  • Have a diet high in fat and low in fiber.

Need To Know:

Who is at risk for inherited forms of colorectal cancer?

  • People whose relatives developed colorectal cancer before age 60.
  • Those with relatives who have other forms of cancer, particularly breast or ovarian cancer.
  • Those with a family history of stomach, abdominal, bowel, bone, or liver cancer. In the past, colorectal cancer was misdiagnosed as stomach, abdominal, or bowel cancer, or, in later stages, the cancer may have spread to the bone or liver.
  • Distant relatives, such as cousins, aunts, uncles, etc., who develop colorectal cancer may raise the risk of colorectal cancer for other distant family members. The relative increase in risk is not as high as in those who have first-degree relatives, such as parents or siblings with colorectal cancer.

Having certain diseases or conditions may place people at increased risk for colorectal cancer. These include

  • Chronic ulcerative colitis, an inflammatory condition of the colon. People in this risk category have long-term disease, most for ten years or more.
  • Crohn's disease, which is an inflammatory disease of the gastrointestinal tract. This disease may increase colorectal cancer risk, although not as much ulcerative colitis.
  • A history of breast, uterine, or ovarian cancer in women.
  • Inherited a specific colorectal cancer syndrome. Those with an inherited syndromes may develop colorectal cancer at a much younger age, in their 30s or even younger.

Inherited Colon Cancer Syndromes

Inherited colon cancer syndromes is a name given to a group of different types of colon cancer found to be directly inherited, or passed down from one generation to the next. Over the past several years, genetic forms of colon cancer have been identified and genetic tests developed.

Need To Know:

Genetic forms of colon cancer represent a smaller percentage of all colon cancer cases. However, those with a strong family history of colon cancer may consider talking to a genetic counselor. Those at high risk may choose to undergo screening at an earlier age.

There are two basic forms of colon cancers recognized as having a genetic basis:

  • Familial adenomatous polyposis (FAP) is a rare genetic disorder of the colon characterized by the development of hundreds of polyps on the inner walls of the colon. People with FAP are at a higher risk for developing colon cancer at an early age (in their early 30s).

    The treatment of choice is to have an operation to remove the diseased colon to avoid the eventual development of colon cancer. This operation can be done without the need for a colostomy.

  • Hereditary nonpolyposis colon cancer (HNPCC) is a form of colon cancer that runs in certain families. HNPCC is divided into two types:
    • Type I: People with this form of HNPCC can develop colon cancer before age 50.
    • Type II: People with this disorder are not only at higher risk for colon cancer before age 50 but are also at high risk for uterine, ovarian, thyroid, bladder, and other cancers.

Nice To Know:

Reliable blood tests can now determine if a person has certain genes responsible for inherited colon cancer. Inherited colon cancer makes up about 20 percent of colon cancer cases.

Gastrointestinal Carcinoid Tumors

Gastrointestinal carcinoid tumors are a rare form of cancer affecting the intestinal tract, including the stomach, small intestine, appendix, colon, or rectum. Carcinoid tumors do not usually cause major, recognizable symptoms and can take years to develop. In most cases, these tumors are accidentally discovered during abdominal surgery. These tumors secrete hormones - groups of chemicals released into the bloodstream that have an effect elsewhere in the body.

In some people, carcinoid tumors may cause symptoms known as "carcinoid syndrome":

  • Facial swelling with redness or flushing
  • Wheezing
  • Diarrhea

Carcinoid syndrome symptoms usually occur only if the cancer spreads to the liver.

Treatment for carcinoid syndrome depends on the stage of the disease and the person's overall health. Treatment may include surgery,radiation therapy, or chemotherapy.

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Colon Cancer

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From Andrew Maynard - Chair of the University of Michigan Department of Environmental Health Sciences, with help from David Faulkner - 2013 Master of Public Health graduate.