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Colon cancer

The colon, or large intestine, serves an important role in digestion and particularly in water absorption.  At its upstream end, the end of the small intestine, or ileum, empties through the ileocecal valve into the "beginning" of the colon, or cecum.  At this point digested matter is in a liquid state.  As the stool goes through the ascending colon, past the hepatic flexure and into the transverse colon, more water is absorbed and the stool becomes more solid.  Passing the splenic flexure, into the descending and sigmoid colon, the stool is now formed.  The rectum serves as a reservoir for formed stool, and the anus acts as a valve to control the passage of stool.  Unfortunately, cancers can develop anywhere alone the way.

Most colorectal cancers begin as polyps, small growths from the wall of the colon that are benign, but can undergo a malignant transformation into colon cancer.  The transformation of polyps in a specified sequence to colon cancer occurs by mutations, or changes, in certain genes that we are just beginning to learn about.  At this point our best defense against colon cancer is early detection and removal of polyps before they can undergo a malignant transformation. People in high risk groups for developing colorectal must be doubly vigilant in their screening program.  It is also important to recognize early warning signs for colorectal cancer, and to report such changes to a doctor or other health professional right away so that appropriate action can be taken.

Certain groups are at higher risk for colorectal cancer.  About 130,000 people in the U.S. were diagnosed with either colon or rectal cancer in 1999. African-American men have the highest incidence of colon cancer compared to others.  Generally the risks for colon cancer are far higher in industrialized nations than less developed countries. This is probably due to environmental factors, including a diet higher in processed foods and lower in fiber.  Well defined genetic mutations present in many Ashkenazi Jews puts those with these gene changes at significantly higher risk than the general population.  Those with relatives with colorectal cancer, especially first degree relatives, are at higher risk.  People who have a sibling or parent who developed colorectal cancer before age 50 have an about 23%  higher risk of colorectal cancer than people whose relatives were free of cancer. People found to have large (over one centimeter) polyps at colonoscopy are also at higher risk. Those with ulcerative colitis and Crohn's disease are also at higher risk. Smoking as well as alcohol use in smokers seems to increase colon cancer risk.

Symptoms of colorectal cancer vary depending upon where in the colon the cancer is located.  Tumors in the cecum and ascending colon rarely obstruct the bowel, but they often lead to chronic blood loss.  This brings about anemia, leading to fatigue, weakness, and heart problems, common presenting symptoms of lesions in this area. Cancers of the transverse colon can lead to obstruction and perforation.  Cancers of the left colon often lead to changes in bowel habits, pencil-thin stools, a feeling of incomplete defecation, and brighter red rectal bleeding.  It is important to recognize, however, that not all rectal bleeding is from colon cancer.  Hemorrhoids, minor tears around the rectal or anal areas (fissures),  diverticulosis, or even certain foods can turn the stools red.  It is critical, however, to promptly have your doctor check out any of the above warning signs.

Dietary and lifestyle factors can help modify the risk for colorectal cancer.  Many experts, supported by clinical studies, indicate that diets low in fruits and vegetables and high in meats increase risk for colon cancer, and that those with diets rich in fruits and vegetables are at lower risk for colorectal cancers. Folic acid, which is found in citrus and green vegetables, has also been found to be protective in some studies.  Diets less laden with saturated fat have been suggested to reduce the risk of colorectal cancer.  Fish oil in the diet appears to lower risk, and monounsaturated oil (olive oil) may have some protective value. It is best to avoid fatty foods and cut down on red meat to lower the risk of heart disease and other unhealthy conditions in addition to colorectal cancer. A number of studies have indicated that regular exercise reduces the risk of colon cancer.

When should people be screened for colorectal cancer? The American College of Gastroenterology recommends the following:

People over 50 should be screened for colorectal cancer by their physician. Several tests are recommended.

  • An annual fecal occult blood test, which checks for minute traces of blood in the stool.
  • A flexible sigmoidoscopy once every 3-5 years to detect colorectal cancer at its earliest and most treatable stage.
  • Frequent colonoscopy is recommended for high risk patients of any age with prior history of cancer, a strong family history of the disease, or a predisposing chronic digestive condition such as inflammatory bowel disease.

It is truly unfortunate that only a minority of patients adhere to the screening guidelines above.  Surveys taken from patients have indicated that fear of pain with the screening tests as well as embarrassment were main causes of patients not sticking to the above schedule.  Most don't realize that new equipment and techniques take most all the pain out of colorectal screening.  The vast majority of people who have their first screening test state that they would not hesitate to have further regular screening.