When to Get a Colorectal Cancer Check

Excluding skin cancer, colorectal cancer is the third most common type of cancer in the United States.   It strikes over 100,000 Americans and kills about 56,000 every year. It's one of the most curable cancers if detected early, but it often produces no symptoms until it's beyond successful treatment. It is thought that colon cancer develops when environmental factors interact with an person’s inherited or acquired susceptibility. Most colon cancers (about 90%) come from a type of growth in the large intestine called adenomatous polyps. These polyps can slowly change, usually taking decades to develop into cancer.

That's why everyone should be aware what risk group they fall into and when to begin screening for colorectal cancer.

All women and men at average risk for colorectal cancer should have a screening test for colorectal cancer beginning at age 50 (colorectal cancer is rarely found in people under the age of 50).

 People who are at higher risk for colorectal cancer may need to begin screening tests at an younger age. People at higher risk include:

• Those with familial polyposis; that is, a family history of development of multiple polyps likely to become cancerous. Although only about 1 percent of all colorectal cancer patients have this gene, those who do have it have a 100 percent chance of developing cancer. People with this cancer will likely die in their 40s if not treated. They should start screening in their teenage years.

• Those with hereditary non-polyposis cancer, which is brought about by defective DNA repair genes. About 5% to 10% of the people with colon cancer have this condition. People with this cancer have parents or siblings who developed colorectal cancer before age 40. They should start screening a few years before the age of the family member who developed colorectal cancer.

• Those who have had colorectal cancer or a precancerous polyp.

• Those who have a parent, sibling, or child who has had colorectal cancer before the age of 60, or if more than one relative is affected (at any age), have a 2 to 4 times greater risk.

• Those who have chronic inflammatory bowel disease (ulcerative colitis or Crohn's colitis) a condition that causes the colon to be chronically inflamed have an increased risk of developing colon cancer. Screening should be started at a young age and be done more frequently.

Several methods can be used for screening. A person’s preference and the recommendation of his or her health care provider should determine which test is used and how frequently a person is screened.

Screening tests

The fecal occult blood test (FOBT) or or fecal immunochemical test (FIT) look for hidden (occult) blood in stool. Blood in the stool can be caused by a variety of conditions; colorectal cancer is only one of them. The FOBT uses a chemical reaction to detect blood in small samples of stool that have been placed on a FOBT sample card. Usually two samples from each of three consecutive stools are collected and mailed or taken to your health care provider’s office for testing. The FIT looks for a specific part of a human blood protein. Collecting samples for the FIT is easier, but the test is more expensive than the FOBT. The American Gastroenterological Association (AGA) says that if a test is positive for blood in stool, a colonoscopy should be done to determine the source of the bleeding. It could be caused by cancer, a polyp, hemorrhoids, diverticulosis (a condition in which small pouches form at weak spots in the wall of the colon) or inflammatory bowel disease (also called colitis). If cancer or a precancerous polyp does not bleed, this test will not detect it. Certain foods or drugs can affect the test, so you should follow instructions on diet and medications. The American Cancer Society (ACS) and the AGA recommend that people at average risk have this test each year.

Sigmoidoscopy uses a short, flexible, lighted tube tube that is inserted into the rectum and gently moved into the lower half of the colon. It is a common screening method, but only covers the lower part of the colon, representing about half the surface at risk for developing cancer. Before this test is done, the colon and rectum must be cleaned with an enema. The ACS recommends that people at average risk have this test every 5 years.

Colonoscopy uses a colonoscope, a slender, flexible lighted tube that is longer than the one used for sigmoidoscopy. In a colonoscopy, the entire colon is examined. If a polyp is found, it can be removed during the colonoscopy. Before a colonoscopy, the entire colon must be cleaned with laxatives and enemas. A colonoscopy can be uncomfortable, so an intravenous medication is used to make you feel sleepy during the procedure. Colonoscopy takes 15 to 30 minutes, longer if a polyp is removed.

A combination of all three tests offers the best protection. For people at average risk, the ACS recommends a combination of tests: an FOBT every year, and a sigmoidoscopy every five years. If either of these is positive, a colonoscopy is recommended. A colonoscopy is recommended every 10 years.

Several newly developed methods of screening for colorectal cancer are being developed but are not recommended as screening options at this time. These include virtual colonoscopy (a CT scan of the colon), and analysis of stool for DNA abnormalities that may indicate the presence of cancer.  

Screening for those at higher risk

The ACS makes the following recommendations:

• If you have had a precancerous polyp or colorectal cancer, you should follow the recommendations of your health care provider.

• If  you have a parent or sibling who had colorectal cancer before the age of 60, or two or more close relatives who had colorectal cancer at any age, you should have a colonoscopy beginning at age 40, or 10 years before the youngest case in the immediate family. Screening by colonoscopy should continue every five years as long as the results do not show a precancerous polyp or cancer.

• If you have  a family history of familial adenomatous polyposis (FAP), you should be under the care of a specialist, and you generally should begin screenings at puberty.

• If you have a family history of hereditary non-polyposis colorectal  cancer (HNPCC), you should be under the care of a specialist, and you generally should begin screening at age 21.

• If you have Inflammatory bowel disease, chronic ulcerative colitis or Crohn's disease, you should be under the care of a specialist who can determine when screening should begin.