What is colon cancer?

Colon cancer is a tumor of the large intestine (colon) that can spread to other parts of the body and cause death. When it spreads it is called metastasis. Colon cancer is the second most common cause of cancer-related death in the United States. Most people with colon cancer get better if the cancer is found early. Rectal cancer is a type of colon cancer that starts at the end of the large intestine (called the rectum). The term “colorectal cancer” is sometimes used for cancer of the colon and rectum. 

What are the symptoms of colon cancer?
 
Colon cancer causes blood in the stool when it is advanced enough to do so, abdominal pain (again when it is in an advanced stage), and a change in bowel movements (for example, a change in the width of your stool). If this is allowed to get worse, sometimes the stools can be so narrow as to be called “pencil stools”. Some people don’t have any symptoms at all. If you don’t have symptoms, it is more likely that the tumor will not be found without screening and will continue to grow. Screening tests can find cancer and small tumors called polyps that are like finger-like projections into the bowel opening that can turn into cancer over time. Some of these are pre-malignant or precancerous. There are some types of polyps that are not pre-cancerous and don’t turn into cancer in the future. 

Who should be screened?

It is recommended that healthy people 50 years and older should get screened. You should continue to get screening until you are 75 years of age, assuming that there have been no abnormalities found to that date and that you are not considered high risk by other criteria. If you have symptoms of colon cancer or if you are at risk of colon cancer, your doctor may suggest getting screened before 50 years of age and as well after 75 years of age. You are at risk of colon cancer if you have a parent, brother, or sister who has had colon cancer, polyps or other less common conditions (for example, inflammatory bowel disease). If you have had pre-cancerous polyps before, that puts you in a higher risk category.

What are some colon cancer screening tests? 

Fecal Occult Blood tests or stool cards. This test is done at home or in the doctor’s office at intervals at a year or more. You take a stool sample from 3 bowel movements in a row and put it on a card that your physician has given you. You take that back to the doctor’s office for testing. This test decreases deaths from colon cancer, but only is positive if the cancer is bleeding, therefore it has low accuracy and works only if it is done every year, or if there is another reason such a dark color of your stool. If the test is abnormal, you will need to have a colonoscopy. 

Colonoscopy – This test is done starting at age 50 and then every ten years as long as there is no reason for it to be done more frequently or earlier. For this test, your doctor will give you a regimen to prepare you before the procedure. You will also obtain intravenous medication at the time of the exam that will make it so that you do not remember the exam. He or she will then insert a thin tube connected to a video camera into your rectum to look at your whole colon. Again, prior to the procedure you will have to take laxatives the day before the test to clean out your colon. That is probably the most important part of your preparation. One must complete all of the laxatives or there may be too much stool left in the colon to get an adequate exam. Keep well hydrated to prevent dehydration. If polyps are found during the test, they can usually be removed right away through the colonoscope. There are no nerve endings there, so that you will not feel any biopsies that might be done. You will probably miss that day of work and someone will have to drive you home after the test. Colonoscopy is the most accurate test to screen for colon cancer, but it is also the most expensive. It does cause more injuries than the other tests (one or two people will be injured for every 5,000 people who have the test). If your colon is injured during the test, you may need surgery to repair it. This is a rare complication.

CT Colonography – This test is also called a “virtual” or “x-ray” colonoscopy. It is a newer test, and the best way to use this has not been decided. Also, how much it costs and how safe it is compared with the other tests needs to be more fully delineated. For this test, compressed air is pumped into your rectum through a tube. Then a picture is taken of your colon. You will have to take laxatives the day before the test to clean out your colon just as with the colonoscopy. This test is almost as good at finding large polyps as colonoscopy, but it is less accurate overall, especially for finding small polyps. If the test is abnormal, you will still need to have a colonoscopy. Obviously if the staff is not ready to do it that day, you would have to have a preparation again before the colonoscopy is done. Radiation exposure may be considerable over the years.

How can I prevent colon cancer?

The only way to prevent colon cancer is to find polyps early and to have them removed. Being obese or not getting enough exercise increases your risk of getting colon cancer. Eating less fat and possibly taking aspirin may lower your risk of getting polyps. But, aspirin may cause gastrointestinal bleeding, kidney problems, and other drug interactions. Before you think about taking aspirin, you need to discuss this with your physician.

Women who have gone through menopause may lower their risk of colon cancer by taking hormones but, hormones have side effects including blood clots and a higher risk of breast cancer. Taking fiber or antioxidants (for example, vitamin A) does not decrease the risk of colon cancer. Vitamin D has been shown not only to improve the strength of bones and increase the immune defenses of the body to ward off infections, but can also decrease several forms of cancer.