By Barbara Entsuah, MD

Colorectal cancer is the third leading cause of death due to cancer in the US. In 2005 according to the American cancer society, 145,000 people were affected. Family history may play a significant risk factor, with about 30% of diagnosed cases showing familiar groupings, meaning that those people may have a definable genetic component. About 3-5% of colon cancers are associated with inherited colon cancer syndromes. Those with ulcerative colitis also have a higher risk. Most colon cancers begin in the large intestines (colon). Rectal cancer begins in the rectum- which is closest to the anus. Most of these cancers begin as a polyp.

WHAT IS A POLYP?

Most polyps start as a small harmless fleshy growth in the wall of the colon or large intestine. However, as a polyp gets larger, it can develop into a cancer that grows and spreads. Polyps are extremely common, and incidence increases with age. About 50% of individuals over the age of 60 years will have at least one polyp. With time a polyp can grow larger and develop into cancer that grows and spread outside the walls and inside the lumen of the colon. It will then spread to nearby lymph nodes and outside to other organs. There are four main different types of colon polyp groups: hyperplastic, Inflammatory, hamartomatous and adenomatous. The most common polyps are adenomatous polyps (account for 75% of all polyps) and they have the potential to develop into cancer. A large polyp has the tendency to be cancerous and when they are about one inch in size, their risk of becoming cancerous is about 20%. It is for this reason that doctors remove polyps during a sigmoidoscopy or colonoscopy. It is then tested for cancer. One is more likely to get polyps if one eats a lot of fatty foods, smokes, drink alcohol, don’t exercise or is overweight. Eating more calcium and folate may lower one’s risk of getting polyps. Some foods rich in folate are peas, leafy greens, spinach, kidney beans.

Recent studies in the journal of American Medical Association have shown that flat colon growths also have potential to be cancerous and cancer have been found in flat or depressed growths. This calls for a careful thorough screening process.

WARNING SIGNS OF COLORECTAL CANCER

These include blood in the stool or toilet bowl after a bowel movement, change in the shape of the stool, pain in the lower abdomen, and change in bowel movements. There can also be other non specific symptoms like weight loss, fatigue, feeling of fullness, anorexia and anemia. However many polyps do not cause any symptoms

RISKS ASSOCIATED WITH THE DEVELOPMENT OF COLORECTAL CANCER

Many studies have examined the relationship between diet and development of colorectal cancer. For total vegetables majority of studies reported that risk was reduced by at least 20% for those in the highest compared with individuals in the lowest intake category. For total fruits the results are not as consistent as with vegetables, and the studies also showed inverse association with risk of distal (lower part) colon cancer compared to proximal part( upper part) of the colon . Fruits and vegetables are rich in many nutrients and bioactive compounds such as folate, fiber, vitamins, and carotenoids that may have cancer preventive properties. Nutrients can also detoxify or deactivate carcinogens (cancer causing substances). Diets rich in fruits and vegetables are important even for other health outcomes like cardiovascular disease and other cancers.

In a February 2003 study published in the Archives of Internal Medicine, women who consumed a high fat, low fiber diet had an increased risk of developing colon cancer compared with those who had a lower fat, high fiber diet. However there was also a reduced risk for those who had a high fiber and healthy protein diet. Western diet consisting of high intake of red meat, sugar desserts, high fat and refined grains have a 3- fold increase in cancer recurrences and death in patients who had colon cancer and had undergone previous treatment.

Other factors associated with increased risk for colon cancer include increased Body Mass Index (BMI), smoking, and second hand smoking.

Factors associated with reduced risk but still needing more studies include high dose Aspirin, and Celebrex- both of which are anti-inflammatory medications. As with any medications, risks and benefits ratios have to be taken into consideration before any of these are used.

A vigorous exercise program has been found to decrease the risk of colon cancer and polyps in men.The good news is that the disease can be prevented if polyps are removed in time before they become cancerous. This is when screening procedures come into play

SCREENING FOR COLON CANCER

Getting a colonoscopy or other colon screening procedure, allows your doctor to spot polyps and take them out of the colon or rectum before they become cancerous. Also, if screening shows cancer, early treatment increases the odds of survival. The U.S. preventive services Task Force (USPSTF) is a credible organization which provides current evidence based preventive care guidance and recommendations. It recommends initiating screening at 50 years for men and women at average risk for colorectal cancer. In those with higher risk e.g. those with a first-degree relative who was diagnosed with colorectal cancer before 60 years of age initiating at an earlier age is suggested. Earlier screening is also suggested for those at very high risk like those with familiar polyposis, ulcerative colitis, or hereditary nonpolyposis colorectal cancer. Those with genetic syndromes may also need genetic counseling or testing.

The appropriate age to discontinue screening is not known because most screening studies involved patients less than 80years of age. However, no matter the age, when there are symptoms suggestive of a bowel problem e.g. bleedinG, an exam has to be performed.

SCREENING OPTIONS FOR COLORECTAL CANCER ARE:

1. Fecal occult blood test: Checks for blood in stool samples. Its done annually. Usually 3 different specimens taken on 3 consecutive stool samples are forwarded to the lab.
2. Flexible sigmoidoscopy: Doctors use a thin, flexible, lighted tube to examine the rectum and lower part of the colon; done every five years.
3. Flexible sigmoidoscopy and Fecal occult blood test combined (See above)
4. Double-contrast barium enema: Patient gets an enema containing barium dye, followed by X-rays of the colon and rectum; done every five years.
5. Colonoscopy: Doctors use a thin, flexible, lighted tube to examine the rectum and entire colon; done every 10 years, unless a polyp is found. Then in this case depending on type and number of polyps removed subsequent colonoscopy may be between one and five years. This procedure usually requires sedation. Each screening procedure has its benefits and potential harms which you can discuss with your primary care physician.
6. Though colon cancer screening is up, many people still aren’t getting tested. Talk to your doctor about getting screening if you are 50 years or older, have any symptoms, or someone in your family has had polyps or colon cancer.