Life Saving Benefits In Colorectal Cancer Screening Tests
By Tyler Kang, MD
The idea behind cancer screening is for screening tests to be able to catch cancer in individuals who are otherwise asymptomatic in the early stages so as to make available more effective therapies. While not all cancers lend themselves to be screened easily, colorectal cancer is one that can be because of its predictable progression from pre-cancerous polyps to malignant tumors.
Cancer Screening Techniques
The simplest forms of colorectal cancer screening, are stool-based tests. This includes guaiac and immunohistochemical tests that detect presence of fecal hemoglobin. While simple to perform, compliance may be low due to need for dietary restrictions in some forms of the test. The drawback with this test is that it is neither diagnostic nor therapeutic, and requires follow-up with additional testing for any abnormal results.
The “gold-standard” for colorectal cancer screening involves the direct visualization of the intestine via endoscopy. There are two forms of endoscopy, sigmoidoscopy, in which the endoscopic camera is passed into the latter half of the colon, or colonoscopy, which reaches into the entire colon. These endoscopic procedures are useful not only in diagnosing malignant tumors, but they are useful in identifying pre-cancerous polyps and removing them before development of actual cancerous lesions.
To avoid the invasiveness of direct endoscopies, specialized cameras the size and form of medicine pills have been developed which can be swallowed and allow visualization of the colon without the discomfort of traditional sigmoidoscopies or colonoscopies. Another method of visualizing the colon is the use of computed tomography (CT), which can render a virtual reconstruction of the colon as well as any tumors or polyps within. However, these procedures still require adequate preparation of the colon, and an actual direct endoscopy will still need to be done if an abnormality is identified for the purpose of obtaining biopsies.
While colorectal cancer screening reduces colorectal cancer rates due to the ability to remove early or precancerous lesions, there has been scant evidence that it improves overall survival. But now we have publication of a large, randomized trial by Schoen et al (New England Journal of Medicine, May 2012) that shows sigmoidoscopies, along with the use of other screening techniques, actually reduces the fatality rates from colorectal cancers. Unfortunately, compliance with colorectal cancer screening is low, ranging from as high as 68% to as low as 30%.
In order for screening to work, the population at large must understand the benefits of these tests. Hopefully, with improved understanding and better public knowledge about these procedures, along with their associated risks and benefits, more lives will be saved as we increase the rates of compliance with these screening tests.
Dr. Kang is a board certified Medical Oncologist and Hematologist with Epic Care, a group of experts in the diagnosis and comprehensive treatment of cancer and blood disorders. www.epic-care.com