March is Colorectal Cancer Awareness Month. This public health advocacy was launched as an awareness campaign in the promotion of colorectal cancer screening in 1999, and has resulted in significantly positive clinical outcomes in the management of the disease. Gastroenterologist Dr. Jun Ruiz of The Medical City gives you the latest updates.
Colorectal cancer (CRC) screening is defined by the U.S. Multi-Society Task Force of Colorectal Cancer (MSTF) as “the process of detecting early stage CRCs and pre-cancerous lesions in asymptomatic individuals with no prior history of cancer or precancerous lesions”.
CRC is an ideal target for early detection and prevention through screening. This screening strategy can save lives, by removing precancerous lesions and curing early stage cancers. This can reduce the cancer risk in an individual by as high as 70 percent.
Since I went home to the Philippines in 2014 after an almost decade of being an active and busy gastroenterologist at Kaiser Permanente California, the system with the highest disease screening rates in America, advocating for colorectal cancer screening has been my priority. The Colorectal Clinic of The Medical City where I am affiliated has been among the leaders of this campaign in Metro-Manila with its symposiums, lay forums, and published educational articles for the general public over the years since 2010, even before the clinic officially opened.
The U.S. Multi-Society Task Force of Colorectal Cancer Latest Consensus Guidelines
The biggest development in the past year in the field of CRC screening is the update of the consensus guidelines by the panel of expert gastroenterologists from the three professional organizations, namely the American College of Gastroenterology, American Gastroenterological Association, and the American Society of Gastroenterological Endoscopy. These societies compose the U.S. Multi-Society Task Force of Colorectal Cancer (MSTF). The latest consensus guidelines were simultaneously published in Gastroenterology Journal, American Journal of Gastroenterology, and Gastrointestinal Endoscopy in July 2017.
The top gastroenterology experts of the Task Force continue to recommend CRC screening starting at the age 50 years in average-risk persons. Clinical evidence continues to validate the age when screening is most appropriate. MSTF also support earlier screening at 45 years for African Americans, based on limited evidence.
Despite the screening age in average-risk individuals pegged at 50 by gastroenterology societies worldwide, it is also recognized that CRC incidence is increasing under age 50. As an astute clinician, thorough diagnostic evaluation of young persons with suspected colorectal bleeding is warranted to rule out the possibility of colorectal cancer. Colonoscopy is generally the test of choice for these diagnostic scenarios, though this is no longer screening.
In the last published consensus of MSTF in 2008, the experts recognized multiple tests as options for CRC screening. These methods were divided into 1) stool-based tests that detect cancer; and 2) structural examinations (colonoscopy and radiographic tests), which both detect cancer and pre-malignant lesions. The guidelines emphasized prevention, rather than early detection, should be the primary goal for most patients. The Asia-Pacific Consensus recommendations for colorectal cancer (2015) as well as that of the local Philippine Society of Gastroenterology followed the American guidelines.
First-tier colorectal cancer screening methods
In the latest consensus guidelines of MSTF, CRC screening tests are now ranked in three tiers, based on performance features, costs, and practical application. The first-tier tests are colonoscopy every 10 years and annual fecal immunochemical test (FIT). Now, colonoscopy and FIT are recommended as cornerstones of screening regardless of how screening is offered. In most offices of American doctors and in the gastroenterology clinics in the Philippines, the sequential approach is often employed, by offering colonoscopy, followed by FIT if patient declines the endoscopic test.
The advantages of colonoscopy include: high sensitivity for cancer and all classes of precancerous lesions in the colorectum; an opportunity where diagnosis and treatment of colonic lesions can be done in one setting; and a long interval between examinations (10 years) in subjects with normal results. One or two negative colonoscopic examinations may signal lifetime protection against CRC. For patients who value the highest accuracy in detection of precancerous lesions and are willing to undergo invasive screening, colonoscopy should be recommended by their physician.
The Fecal Immunochemical test (FIT) is a very good screening test, as it detects only human globin and is specific for bleeding in the colon. The advantages of FIT are its non-invasive nature, its one-time sensitivity for cancer of 79 percent, and low one-time cost. FIT is recommended annually in the U.S. and in Asia. FIT is commonly the test of choice in programmatic screening, and an excellent second-choice for practitioners using sequential testing who offer colonoscopy first. Its disadvantages include repeated testing, and poor sensitivity for pre-cancerous lesions.
Colonoscopy and FIT are recommended as tests of choice when multiple options are presented as alternatives. A risk stratified approach is also appropriate, with FIT screening in populations with low prevalence of advanced neoplasia, and colonoscopy in high prevalence populations.
Other screening methods
The second-tier tests include CT colonography every 5 years, the FIT-fecal DNA test every 3 years, and flexible sigmoidoscopy every 5 years. Theses tests are appropriate screening tests, but each has its disadvantage relative to the tier 1 tests.
The flexible sigmoidoscopy (FS) had been discontinued in Kaiser in 2008, and I had eventually anticipated its decline elsewhere. Here in the Philippines, I have not encountered a gastroenterologist who had offered this method as primary screening in the last four years. The advantages of FS include a lower cost and risk, a more limited bowel preparation, and no need for sedation as compared with colonoscopy. Its disadvantages include lower benefit in protection against right-sided colon cancer, and the absence of sedation results in low satisfaction experience for the patient.
CT colonography (CTC, formerly “virtual colonoscopy”) has replaced doublecontrast barium enema as the test of choice for colorectal radiographic imaging. CT colonography is more effective than barium enema, and better tolerated by patients. Radiation exposure is viewed as a disadvantage of this test. This test is only available in a few centers in Metro-Manila.
The U.S. FDA approved Cologuard, a screening test that is a combination of FIT and markers for abnormal DNA. The FITfecal DNA has a one-time sensitivity for CRC of 92 percent. The major disadvantage of the tests is the substantial decrease in specificity (86-89 percent compared to 96 percent for FIT), and the high cost relative to FIT. This test is not available in the Philippines.
Capsule colonoscopy every 5 years is a third-tier test. It is approved for imaging the proximal colon in patients with previous incomplete colonoscopies and more recently for patients who need colorectal imaging but are not candidates for colonoscopy or sedation. It is not approved for screening average-risk patients. It is not available in the Philippines, and its cost would be prohibitive.
A common statement made with regard to CRC screening is that “the best test is the one that gets done”. It is generally better for any person who is eligible to be screened to undergo some screening test rather than not to be screened at all.
March 2018 Health and Lifestyle