Colorectal cancer

WEB EXCLUSIVE / SEPTEMBER 2005
POSTGRADUATE MEDICINE
Update of a handout originally published on May 1, 2000

Download this Patient Note in PDF format

Screening for cancer of the colon or rectum (colorectal cancer) should be a regular part of physical examinations for everyone over age 50 and for some younger people who have a family history of cancer. Early detection can save many lives each year.

What is colorectal cancer?
Cancer is actually a group of diseases that occur when cells in the body change and grow out of control. In most types of cancer, these cells form a mass or tumor. Cells from the tumor may break away and move to other parts of the body. This spreading process is called metastasis.

Colorectal cancer can start in either the colon (the first 6 feet of the large intestine) or the rectum (the last 8 to 10 inches of the large intestine). Before cancer develops, early changes often can be seen in the lining of the last part of the colon (sigmoid colon) or the rectum. One type of change is a growth called a polyp, and removing the polyp early may prevent cancer from developing. More than 95% of colorectal cancers are a type called adenocarcinomas, and most of these start out as polyps.

What causes colorectal cancer?
We don't know the exact causes yet, but we do know there are certain risk factors involved. In general, these include:

• Age. Colorectal cancer is more likely to occur after age 50, although it can occur at younger ages, sometimes even during the teenage years.
• Lifestyle. Diets high in fat and calories and low in fiber have been linked with colorectal cancer. Lack of exercise also seems to play a role.
• Polyps. These benign growths on the inner wall of the colon and rectum are fairly common in people over age 50 and may increase the risk of colorectal cancer. A rare inherited condition called familial polyposis causes hundreds of polyps to form in the colon and rectum. Unless this disorder is treated, it will almost always lead to colorectal cancer.
• Medical history. Women who have had cancer of the ovary, uterus, or breast have a somewhat greater chance that colorectal cancer will develop. Also, colorectal cancer can recur.
• Family history. Parents, siblings, and children of people who have had colorectal cancer are somewhat more likely to have it themselves, especially if the relative had colorectal cancer at a young age.
• Ulcerative colitis. This is a condition in which the lining of the colon becomes inflamed. Chances that colorectal cancer will occur are increased when this inflammation is present.

How is colorectal cancer detected?
People who have a family history of colorectal cancer should ask their doctor when to begin checking for the disease, what tests to have, and how often to have the tests. The doctor may suggest one or more of the following procedures. These tests can detect polyps, cancer, or other abnormalities, often before symptoms are present.

• Digital rectal exam. This is a simple test in which the doctor inserts a lubricated, gloved finger (digit) into the rectum to feel for abnormalities.
• Fecal occult blood test. Sometimes cancerous tissue or polyps bleed. This test detects even very small amounts of blood in the stool.
• Flexible sigmoidoscopy. This examination of the rectum and lower part of the colon, called the sigmoid colon, uses a slender, flexible lighted instrument called a sigmoidoscope. The doctor can look at the inside of the rectum and the last part of the colon to see if any polyps are present. The examination can be watched on a video display.
• Colonoscopy. For this test, a longer flexible tube is inserted into the rectum and passed on to the colon. The tube is long enough to reach the full length of the colon and is attached to a video camera and display. Polyps can be removed by using a wire loop that goes through the tube. Pieces of a polyp or other tissue can be sent to a lab to see if cancer cells are present.
• Double-contrast barium enema. For this test, the patient is given a barium enema that partly fills up and opens the colon. Air is then added to expand the colon, and x-rays are taken. Double-contrast barium enema is less effective than colonoscopy and is not widely used for colorectal cancer screening.

Your doctor can tell you which tests are best for you and how often you should have them. For persons at average risk, the preferred approach is a colonoscopy to screen for cancer every 10 years beginning at age 50. An alternative strategy consists of an annual fecal occult blood test and a flexible sigmoidoscopy every 3 to 5 years.

Recognizing the symptoms Talk with your doctor if you notice any of the following: A change in bowel habits Diarrhea, constipation, or a feeling that the bowel does not empty completely Blood, either bright red or very dark, in the stool Stools that are narrower than usual General abdominal discomfort, such as frequent gas pains, bloating, fullness, or cramps Weight loss with no known reason Constant tiredness Vomiting These symptoms may be caused by colorectal cancer or by other conditions. It is important to check with your doctor.

This information is not a substitute for medical treatment.

Please send technical questions related to the Web site to Ann Harste