Routine screening allows for the early detection of colorectal cancer while it is still highly curable, as well as the detection of growths, or polyps, that might eventually become cancerous.
The disease affects tens of thousands of Americans each year, most of which develop the disease after age 50. “Colorectal cancer occurs in approximately 130,000 Americans yearly,” says Dr. Bennett Roth, chief of clinical gastroenterology, director of the Digestive Disease Center and medical director of the UCLA Center for Esophageal Disorders. “It is the third most common cancer and the third leading cause of cancer death in women and second most common in men.”
Smart Business spoke with Roth about colorectal cancer, who should be screened and what procedures are available.
What is colorectal cancer?
Colorectal cancer (CRC) is a malignancy arising from the lining of the colon or rectum that, if undiagnosed and untreated, will potentially lead to obstruction of the bowel, bleeding and/or spread to vital organs, such as the liver. The majority of CRCs begin as benign polyps, which may mutate over time into malignancies. While, perhaps, no more than two out of 1,000 polyps become malignant, there is no way to know which of these will, and therefore, it is recommended that most polyps be removed, once they are identified.
What are the symptoms of colorectal cancer?
Many colon cancers may be asymptomatic and discovered only at the time of screening. Presenting symptoms include abdominal pain, change in bowel pattern, rectal bleeding or iron deficiency anemia. Unfortunately, the prognosis o those patients presented with such symptoms is less favorable than when this disease is found in an earlier, asymptomatic stage.
Who should be screened?
It is recommended that everyon be screened for this disease. The primary goal of screening is to discover the forerunners of cancer, i.e. polyps or, at the least, cancer in its earliest stages. For those individuals lacking significant increased risk factors, screening is recommended initially at age 50. For those with first-degree relatives having history of CRC diagnosed before age 60, screening should be initiated at age 40. For those with two or more first-degree relatives having CRC or a first-degree relative with early onset CRC (before age 50), screening should begin at an age equivalent to 10 years prior to the age of onset of the relative's cancer. Follow-up screening is dependent upon the findings at the time of the index examination as well as the type of screening performed.
What types of screening tests are available?
Fecal occult blood testing (FOBT) is recommended yearly. If positive, a full colonoscopy is recommended. This strategy leads to a reduction of mortality from CRC of 33 percent over 13 years. Unfortunately, while the sensitivity of the test is high greater than 90 percent the specificity is low. Therefore, the major benefit of this strategy is in identifying those in need of a colonoscopy.
Flexible sigmoidoscopy is a limited endoscopic examination of the rectum and lower portions of the colon. It is often combined with FOBT as a screening strategy. Unfortunately, 40 to 50 percent of polyps may arise proximal to the reach of this examination and, if unassociated with a positive FOBT, may be undetected.
Barium enema is a relatively limited and rarely used means of screening. There are no studies demonstrating efficacy of this modality although it is included in the list of available screening tests.
Colonoscopy has become the primary screening modality for most patients. It has greater than 90 percent sensitivity and affords the opportunity for obtaining biopsies as well as the removal of polyps.
What is the appropriate interval level for follow-up screening?
For average-risk patients, if no polyps are found, repeat examination at 10-year intervals is recommended until age 80 unless medical co-morbities indicate potential reduction in life expectancy or excessive procedural risk to warrant cessation of screening. If polyps are detected, follow-up examinations may be recommended at three- to five-year intervals, depending upon the number, size and type of polyps discovered. If a cancer is found and treated, a follow-up colonoscopy should be done at the one-year anniversary and, if negative, at three years and every five years thereafter. For those at increased risk (family history of sporadic CRC), screening at five-years intervals is recommended. For those with extremely high risk (familial cancer syndromes), screening every two years may be recommended.
How helpful are these tests in detecting colorectal cancer in its early stages?
Screening has been shown to reduce the incidence and mortality of CRC by as much as 35 to 75 percent. Unfortunately, only 45 to 55 percent of adults in the U.S. have been appropriately screened. This is the result of many factors including lack of public awareness, fears and concerns about the nature of screening tests, physician apathy, and inadequate insurance or third-party coverage. The statistics are even worse for racial and ethnic minorities.
DR. BENNETT ROTH is chief of clinical gastroenterology, director of the Digestive Disease Center and medical director of the UCLA Center for Esophageal Disorders. Reach him at BRoth@mednet.ucla.edu.
Chief, clinical gastroenterology
Director, Digestive Disease Center
Medical director, UCLA Center for Esophageal Disorders