Screening and Surveillance for Colorectal Cancer
Colorectal cancer is the fourth most common non-skin cancer, affecting all ethnic groups. About 140,000 people will be diagnosed with colorectal cancer each year and more than 50,000 will die; the lifetime risk is 1 in 20 (5%). An increased risk of developing colorectal cancer is present if there is a personal or family history of colorectal cancer. A personal history of breast, uterine, or ovarian cancer also increases one's risk of developing colorectal cancer. A personal or family history of colonic polyps also increases that risk. Both Crohn's disease and ulcerative colitis may make colorectal cancer more likely after having the disease for a number of years.
Why should people be screened?
Colorectal cancer rarely causes symptoms in its early stages. Colon cancer usually starts out as a benign polyp. Colon polyps can be both precancerous and non-precancerous. Polyps can be detected by screening tests and can be removed, thus preventing colorectal cancer. Early cancers can be cured in up to 90% of cases. Once colorectal cancer causes bleeding, change in bowel habits, or abdominal pain, it has usually progressed to a more advanced stage where less than 50% of patients are cured.
What screening tests are available?
Fecal occult blood testing checks several stool samples for invisible amounts of blood from a colorectal polyp or cancer. If it is positive, a colonoscopy (see below) is needed.
Colonoscopy uses a long, flexible instrument to evaluate the lining of the colon and rectum; abnormal areas may be sampled or removed and sent to the lab for testing. Safe and effective, colonoscopy is the most commonly recommended screening test, because the whole colon is seen and pre-cancerous polyps can be removed, preventing colon cancer. Colonoscopy is the "gold standard" for colorectal cancer screening.
Flexible sigmoidoscopy allows a physician to look at the lower third of the colon, where about half of all polyps and cancers are found. If an abnormality is found, a colonoscopy is then needed. Fecal occult blood testing and flexible sigmoidoscopy are often combined for colorectal cancer screening. However, colonoscopy is considered the optimal method of screening when the test is available and there is no medical contraindication.
An air-contrast barium enema is an X-ray test in which the colon is filled with air and dye to make the lining visible. It is mostly used only if a complete colonoscopy cannot be done.
Virtual colonoscopy combines CT scan images of the air-filled colon into pictures that look like a colonoscopy. If abnormalities are found, colonoscopy is then necessary. It is also useful in patients who have an incomplete colonoscopy. However, most insurance plans as well as Medicare may not cover this procedure.
What are the screening recommendations?
For people with no risk factors, screening starts at age 50. Having a colonoscopy every 1 O years is considered the gold standard. Flexible sigmoidoscopy every 5 years with yearly stool occult blood testing is an acceptable alternative when a colonoscopy is not feasible.
People with a close relative (parent or sibling) with colorectal cancer or polyps will start screening at age 40, or 10 years before the youngest age at which a relative was diagnosed. These patients will often undergo screening every 5 years, even if their test is normal.
Less common types of inherited colon cancer (hereditary non-polyposis colon cancer and familial adenomatous polyposis) may require much more frequent screening, beginning at a much earlier age.
What are the surveillance recommendations?
People who have precancerous polyps completely removed should have a colonoscopy every 3 to 5 years, depending on the size, type, and number of polyps found. The exam interval will usually depend upon the pathology of the growth removed. If a polyp is not completely removed by colonoscopy or surgery, another colonoscopy should be done in 3 to 6 months.
Most colorectal cancer patients should have a colonoscopy within 1 year of its initial removal. If the whole colon could not be examined prior to surgery, then colonoscopy should be done within 3 to 6 months. If this first surveillance is normal, then colonoscopy should be done every 3 to 5 years.
Patients with ulcerative colitis or Crohn's disease for 8 or more years should have a colonoscopy with multiple biopsies every 1 to 2 years.