Starting at age 50, screening tests for colon cancer are recommended for everyone of average risk. Individuals with a personal or family history may need screening earlier or more often. Researchers report that pre-cancerous polyps can be detected and removed 10 to 15 years before colon cancer develops. Thus, after a colonoscopy most of us can expect to hear, “Come back in 10 years.” So do we need to keep this up forever? If I live to be 100, I don't think I want any more screening tests for slow growing cancers. What about 90-year-olds? Or healthy folks at 80, or even 70, who have no history of colon cancer or polyps?
A recent paper from Duke University in North Carolina explored the risks and benefits of screening older patients for colon cancer. The risk of developing this cancer increases with age, but the risk of death from it decreases. Older people are more likely to die of other causes, such as cardiovascular disease. Thus, the benefits of screening decrease with age. At the same time, screening tests carry their own risks that increase with age.
Colonoscopy is probably the most widely recognized screening test, since it provides the opportunity for the physician to remove polyps as well as diagnose colon health in the same procedure. It is generally done with sedation, and always requires bowel preparation with electrolyte and polymeric laxatives. The risks include bowel perforation, bleeding, and complications from the drugs used. Older people are more sensitive to sedative drugs, and are more likely to suffer breathing problems or aspiration. Patients with renal or cardiac disease may have complications from the preparation as well.
The American Cancer Society provides a detailed online comparison of screening tests:
1. Colonoscopy
2. Sigmoidoscopy
3. Computed tomography colonography (virtual colonoscopy)
4. Double contrast barium enema
5. Fecal occult blood test
6. Fecal immunochemical test
7. Stool DNA tests
The less invasive tests have their own disadvantages. Fecal tests can produce false positive results, which may be especially disturbing to older patients with cognitive impairment. Sigmoidoscopy, CT colonography, and double contrast barium enema must be followed up with a colonoscopy if polyps are found.
Reference 1 suggested that patients over age 75 should consider carefully whether colon cancer screening is worthwhile.
References:
1. Wilson JA, “Colon cancer screening in the elderly: When do we stop?”, Trans Am Clin Climatol Assoc. 2010; 121: 94-103.
2. American Cancer Society information on colon cancer screening methods:
http://www.cancer.org/cancer/colonandrectumcancer/detailedguide/colorectal-cancer-detection
Linda Fugate is a scientist and writer in Austin, Texas. She has a Ph.D. in Physics and an M.S. in Macromolecular Science and Engineering. Her background includes academic and industrial research in materials science. She currently writes song lyrics and health articles.