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Risk Factors For Colon Cancer

Updated on February 12, 2016

Herediary Risk Factors For Colon Cancer

Image Reprinted from Gastroenterology, Vol 119, No.3 Randall W.Burt, Colon Cancer Screening , Pages 837-853, Copyright (2000); With Permission from Elsevier
Image Reprinted from Gastroenterology, Vol 119, No.3 Randall W.Burt, Colon Cancer Screening , Pages 837-853, Copyright (2000); With Permission from Elsevier | Source

Colon cancer commonly occurs in individuals 50 years of age or older. Most of these, regardless of their cause, are believed to arise from adenomatous polyps. A polyp is a grossly visible protrusion on the inner lining of intestines. Only a minority of such lesions ever develop into cancer, while most polyps produce no symptoms, and remain undetected.

The probability of an adenomatous polyp becoming cancer depends on the following factors:

  1. Flat based or sessile polyps are more likely to turn cancerous, as compared to the stalked or pedunculated ones.
  2. Villous polyps with a papillary structure have an increased malignant potential, as compared to those with a tubule-like microstructure.
  3. Large sized polyps more than 2.5 cm in size are more likely to house invasive cancer, as compared to smaller polyps with size less than 1.5 cm.

Following detection of an adenomatous polyp, the entire large intestine should be visualized endoscopically, to look for synchronous lesions elsewhere. Colonoscopy should be repeated periodically, even in the absence of cancer.

A risk factor is anything that affects your chance of getting a disease. Main risk factors for the development of colon cancer, include the following:

1. Age

The incidence rises sharply after age 40, and most individuals with this disease are over age 50.

2. Personal history of other cancers

Individuals with the history of a treated colon cancer, are at risk of developing a second one.

3. Family history

The risk of colon cancer is proportionate to the number of affected first-degree relatives. A person having one family member with colon cancer has a three-fold increased risk; if the affected family member was under 55 years age when the cancer was detected, then the chances are much greater. An increased risk is also found in close relatives of people with adenomatous polyps detected before age 60.

Red Meat Cooked At Very High Temperatures Increases Colon Cancer Risk


4. Diet

The disease occurs more often in the upper socio-economic class, especially those who live in urban areas. There is a direct correlation between this cancer and increased intake of high-calorie energy dense food, meat protein, dietary fat and oil, elevations in serum cholesterol, and the presence of heart disease. According to the Mayo clinic, some studies have found an increased risk in people who eat diets high in red meat. Processing and cooking meats at very high temperatures further increase this risk. Regular intake of animal fat in large quantities leads to an increased proportion of harmful microbes, the anaerobic bacteria in the gut microflora. These harmful bacteria produce certain toxins that convert the bile acids (secreted by the liver and stored in the gallbladder) into poisonous carcinogens, the harmful chemicals that initiate cancer formation. Individuals whose diet is high in roughage, produce more frequent and bulkier stools and have a low incidence of large intestine cancer. The theory that supports cancer protective effects of fiber suggests that, fiber present in the food accelerates the intestinal transit time, that is, it speeds up the intestinal propulsive and mass movements, that propel the semi-digested food forwards, thereby reducing the exposure of inner lining of colon to potential cancer-causing toxins, and diluting the carcinogens due to increased fecal bulk. This theory has been subject to doubts, because although an enhanced fiber intake increases the bulk of stools, there is no confirmatory and consistent evidence that a higher fiber intake consistently shortens the stool transit time.

5. Hereditary factors

Many individuals suffering from colon cancer have a family history of the disease, suggesting a hereditary predisposition. Increased risk in siblings and children of an affected individual, is both due to environmental and genetic factors. The hereditary factors that increase an individual's risk of suffering from cancer colon include the following:

  • Polyposis Coli or Familial Polyposis of Colon: This is a rare hereditary condition characterized by the appearance of thousands of small protrusions or adenomatous polyps throughout the large intestines. This disease is a rare cause of colon cancer. The occasional individuals who do not have an affected family member, develop this condition due to a spontaneous mutation, that is, a stable, heritable change in their DNA or the genetic material. In this condition, the genes that normally hamper the growth of cancer cells called the tumor suppressor genes, are absent. Polyps are rarely present before teenage but are generally evident in an affected individual by age 25. If the polyps are not treated surgically, then colon cancer will develop in almost all individuals with polyposis before age 40. The children of an affected individual have a 50% risk of developing this disorder, and should be carefully screened at regular intervals. Two distinct syndromes form a subset of Polyposis Coli and include the Gardner's syndrome characterized by the presence of soft tissue and bony tumors, and cancer ampulla, in addition to the polyps; and Turcot's syndrome with the presence of tumors in the brain and spinal cord, along with colonic polyps.
  • Hereditary Non-Polyposis Colon Cancer (HNPCC): Also known as Lynch syndrome, this condition is associated with tumors in the initial parts of large intestines, as well as in uterus, ovaries, kidneys, pancreas, stomach, and small intestines. In this condition, the median age for the appearance of colon cancer is under 50. It has a predilection for the right colon. Amsterdam's criteria for Non-Polyposis Colon Cancer include - Presence of three or more relatives with colon cancer in the family, one of whom is the first-degree relative of the other two; Cancer diagnosed before age 50 in the family; Involvement of at least two generations with the disease. Such individuals are afflicted by multiple cancers. Women with this condition are at an additional risk of cancers of ovaries or the uterus. Members of families with this genetic condition should undergo biennial colonoscopy, beginning at age 25, with additional intermittent pelvic ultrasound, transvaginal ultrasound, and an aspirate of inner lining of the uterus, for women.

6. Inflammatory Bowel Disease

Large intestinal cancer can occur as a complication in people with long-standing inflammatory bowel disease. Cancers appear to develop more commonly in individuals with Ulcerative colitis, than in those with Crohn's disease. Cancer risk is relatively small during the initial 10 years of disease, but then it appears to steadily increase every year. The risk is higher if inflammatory bowel disease occurs at a younger age, and involves the entire colon. The detection of cancer in these individuals is an extremely complicated situation, as the symptoms like blood filled diarrhea, abdominal cramping and obstruction, which may signal the appearance of a tumor, are similar to the complaints caused by flare-ups of the underlying disease.

7. Septicemia

For unknown reasons, individuals who develop septicemia, that is, the spread of harmful bacteria or their toxins via the bloodstream, or an infection of the inner lining of the heart (endocarditis) due to the fecal bacteria Streptococcus Bovis, have a high incidence of cancers of the digestive tract.

Cigarette Smoking is an independent risk factor


8. Ureterosigmoidostomy

Individuals who have undergone this procedure are at a risk of suffering from colon cancer, some 15-30 years later.

9. Tobacco use

Cigarette smoking, particularly after 30 years of tobacco use, is associated with an increased risk of this cancer.

10. Other risk factors

Individuals with a personal or family history of gynaecological cancers (ovaries, uterus, cervix) or diabetes, have a moderately increased risk. Obesity, physical inactivity, excessive alcohol consumption, and radiation therapy to treat previous cancers, also add to this risk. A new research suggests that women who work a night shift at least three times in a month, for 15 years or longer, are at an increased risk of colon cancer. This study needs to be investigated further.


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    • Larry Rankin profile image

      Larry Rankin 2 years ago from Oklahoma

      So many carcinogens out there. Wonderful overview.