Colorectal cancer: sigmoidoscopy or colonoscopy
The tests: A fecal occult blood test simply requires a stool sample to check for blood. In two other screenings — sigmoidoscopy and colonoscopy — you must drink a preparation that purges your system. Then the doctor inserts a thin tube equipped with a tiny camera into the bowel to look for precancerous or cancerous growths. A sigmoidoscopy inspects only the lower colon, but a colonoscopy examines the entire colon.
The guidelines: The task force recommends screening with any of the three tests for people ages 50 to 75. Testing regimens, it says, can include a yearly fecal occult blood test, a sigmoidoscopy every five years with fecal occult blood testing every three years, or a colonoscopy once a decade. Another group, the U.S. Multi-Society Task Force on Colorectal Cancer, ranks the screening methods, saying tests like fecal occult blood screens can detect early stage cancers, but the colonoscopy is considered a method for prevention.
What to consider: Scientific evidence supports the lifesaving potential of both fecal occult blood tests and, to an even greater extent, sigmoidoscopy, which may reduce colorectal cancer deaths by more than 40 percent. For years colonoscopy has been considered the gold standard of colon cancer screening in the United States, because it looks at the entire colon. But recent observational studies cast doubt on whether colonoscopy cuts mortality any more than the simpler sigmoidoscopy. Patient preference is key because both of these tests are more rigorous than many other health screenings. Sigmoidoscopy requires somewhat less purging of the bowel beforehand, and generally no sedation, so the patient can get home unaided. On the other hand, some patients may prefer the sedation that helps them remain relaxed or sleep through a colonoscopy.
The bottom line, says Sidney J. Winawer, M.D., a gastroenterologist at Memorial Sloan-Kettering Cancer Center in New York and former chair of the Multi-Society Task Force, is that any of the recommended tests is far better than no test at all. "The best test is the one that gets done well," he says.