Colorectal cancer is the second-leading cause of cancer death in the United States. By the time a person shows symptoms of the disease, cancer of the large intestines and rectum may be difficult to treat successfully.
However, screening procedures such as colonoscopy can detect precursors to colorectal cancer long before symptoms appear, meaning treatment is more likely to be effective. Although colonoscopy is still the most common method of screening in this country, newer technologies and medical advances are providing alternatives for some patients. This is good news for those who worry that a colonoscopy or its preparation might be uncomfortable or poorly tolerated.
Risk categories
Screening guidelines for colorectal cancer vary, depending on whether a patient is at average or increased risk of the disease.
- A person at average risk has no chronic bowel-related illnesses, for example Crohn’s disease or ulcerative colitis, or family history of advanced polyps or colorectal cancer. Screening usually begins at age 50 and is repeated every 10 years until age 75. At that point, if all screens have been negative, the risks of the test start to outweigh the likelihood of identifying lesions that may lead to cancer. African-Americans have a slightly higher risk and should begin screening at age 45.
- A patient has an increased risk of colorectal cancer if he or she suffers from a bowel-related illness such as inflammatory bowel disease or has a parent or sibling who was diagnosed with colorectal cancer or identified with advanced colon polyps. These patients should begin screening at age 40, or 10 years before the earliest age that a relative was diagnosed, whichever is earlier, and should continue every five years.
Alternative screening methods
Colonoscopy remains the most-used screening method in the U.S. because it in nearly all cases examines the entire colon and is the only method that is also therapeutic, enabling removal of any polyps detected. However, because it is an invasive procedure, it does carry a slight risk for some patients. These risks, as well as a patient’s additional health issues, are discussed with the patient if this approach is recommended.
Patients can discuss alternative screening methods with their physician to determine whether one might be appropriate, based on their personal risk of colorectal cancer and other medical indicators. Most alternative methods do need to be conducted more often than a colonoscopy, and patients should realize that, if a test result is positive, a colonoscopy would still be required for further diagnosis and treatment. Also, some health insurance might not cover all types of screening tests.
Current alternative screening methods include:
- Guaiac fecal occult blood test (gFOBT). The patient collects a stool sample at home and brings it to the medical office, where the staff uses a chemical to test for the presence of the blood protein hemoglobin. This requires annual testing.
- Fecal immunochemical test (FIT) also is based on a home-collected stool sample and uses antibodies to look for hemoglobin protein. This requires annual testing.
- Fecal DNA test (FIT-DNA) detects tiny amounts of blood in the stool plus nine DNA biomarkers for colorectal cancer and precancerous advanced adenomas. Cologuard is the only U.S. Food and Drug Administration-approved version of this test to date. This requires testing every three years.
- Virtual colonoscopy, also known as computed tomographic (CT) colonography, uses a CT scanner to produce images of the colon and rectum from outside the body. Although the patient does not need to be sedated, rigorous bowel prep is still required. This requires testing every five years.
- Capsule endoscopy is a noninvasive procedure for imaging the upper part of the colon as may occur with an incomplete colonoscopy. The patient swallows a vitamin-sized wireless capsule that takes pictures as it travels through the digestive system and sends the images to a recorder the patient wears on a belt. This requires a more rigorous bowel preparation. Currently this is not indicated for routine screening as an alternative to standard approaches described in this article.
- Sigmoidoscopy is similar to a colonoscopy, but only the lower portion of the colon is examined; polyps there can be removed during the procedure. The patient usually is not sedated. The bowel prep for this test is less extensive than with a colonoscopy. It is often coupled with stool testing for occult blood.
- Double-contrast barium enema (DCBE) X-rays the colon and rectum after the patient is given an enema with a barium solution that outlines the organs. This test does not detect the smallest cancers and polyps but is still used for some patients who cannot undergo a colonoscopy. This requires a thorough bowel preparation.
Regardless of the method used, it’s important to follow health care provider’s recommendations for colorectal cancer screening. While some screening methods can be uncomfortable due to the bowel preparation, a short period of discomfort is a small price to pay for early detection that unquestionably saves lives.
Nicholas Inverso, MD, is a gastroenterologist with Penn State Endoscopy Center in State College. To make an appointment call (814) 272-4445.
