Colorectal cancer is the third most common cancer affecting both males and females in the United States; approximately 70 percent of cases arise in the colon . Globally, colorectal cancer is the third most commonly diagnosed cancer in males and the second in females; however, the incidence varies markedly
Colon is a term for large intestine that carries stool or waste products to the rectum. Colon is highly contaminated by bacteria and is also the site where food reaches after the absorption of nutrients; it is here that the liquid stool is converted to solid waste. Therefore it is speculated that the longer the solid wastes stay in the colon, longer is the time for exposure of cancer forming substances to the lining of colon.
The patients with colon cancer present with the main symptoms of rectal bleeding, change in bowel habits, weight loss, diarrhea, and pain.
Studies have shown that people who consume high fiber diet, diet rich in fruits and vegetables and low in red meats, especially processed meats (burgers, hot dogs) have significant protection. Choose fish, poultry, or beans as an alternative to beef, pork, and lamb; when eating meat, select lean cuts and have smaller portions, using meat as a side dish; prepare meat by baking, broiling, or poaching, rather than frying or charbroiling, to reduce the overall fat content. High-fat diets have been associated with an increase in risk for cancer of the colon.
Folate, a vitamin, which is found in most fruits and vegetables, has been found to be beneficial. A recent report indicated that the excess risk of colon cancer among women with a positive family history of colorectal cancer could be substantially reduced if they had high intakes of folates or a multivitamin supplement.
Calcium supplementation has also been advocated as decreasing the risk for colon cancer, the method may be by Calcium binding harmful acids thus decreasing the exposure of the colon lining to cancer forming substances. Thus a multivitamin containing Folate and Calcium may be the most efficient way of obtaining these nutrients and preventing colon cancer, besides the dietary habit mentioned above.
Aspirin and Anti-inflammatory drugs also offer significant protection against the development of colon polyps.
Physical inactivity (increases the transit time of solid wastes), obesity, central deposition of fat and over consumption of energy has consistently been shown as the major contributor of higher rates of colon cancer in Western countries.
High alcohol intake has been consistently related to higher risk of colorectal adenoma. A recent meta-analysis indicated that high consumers of alcohol had an elevated risk of colorectal cancer.
Tobacco appears related both to rectal and colon cancers. Based on estimates from various studies of the population attributing the risk of colorectal cancer to smoking, approximately 7,000 to 9,000 deaths from colorectal cancer per year in the United States are attributable to smoking.
Polyps in the colon and rectum are forerunners to cancer and the time taken for a normal colon lining to turn into a polyp and then to cancer takes approximately ten years, which indicates that there is ample time to screen colon cancer. Several methods are used to detect cancer/precancerous polyps and to remove them. These are Stool testing for blood, Flexible sigmoidoscopy, Colonoscopy and Double Contrast Barium Enema. Modern techniques include Virtual Colonoscopy, Stool tests for genetic markers, Computed Tomography and Magnetic Resonance Imaging. The accuracy of these tests differ, and of all Colonoscopy is the most sensitive and specific to detect colon cancer and the American College of Gastroenterology advocates Colonoscopy as the screening procedure of choice. Early Removal of polyps during Colonoscopy results in 76 to 90% reduction in the incidence of cancers. Virtual Colonoscopy, CT and MRI need to pass the test of time and require more studies to prove their efficacy as new questions arise with the emergence of these new techniques.
In general, the average age for screening colon cancer is 50 years. In patients who have history of polyps detected by colonoscopy, their physician will customize screening every 3 to 5 years as per the recommendation. In patients who have a family history of colon cancer, screening should begin at the age 40 or 10 years prior to the detection of cancer in their relative whichever is earlier. In patients who have a family history of Familial Adenomatous Polposis, and in patients who suffer from Crohn’s Colitis and Ulcerative colitis, screening may be required at a much earlier age.
The mainstay of treatment of colon cancer is surgery. It may involve removal of the diseased colon followed by reconnecting the cut ends, however sometimes reconnection is not possible and then the cut end of the colon opens to the outside of the abdominal wall for passage of stool called colostomy. Chemotherapy may also be used as treatment for colon cancer especially to prevent cancer recurrence.
Screening the average risk population over the age of 50 has been shown to reduce mortality from colon cancer by 50%, thus timely screening for colon cancer will prevent one of the most common cancers of our times.
The overwhelming evidence indicates that primary prevention of colon cancer is feasible. At least 70% of colon cancers may be preventable by moderate changes in diet and lifestyle. Secondary prevention, through screening by sigmoidoscopy and colonoscopy, is also critically important to prevent death from colon cancer. However, many of the diet and lifestyle risk factors for colon cancers are the same for heart disease and for some other cancers, so focusing on the modifiable risk factors for colon cancer is likely to have many additional benefits beyond this cancer.