By Sue Rochman
Colonoscopy’s effectiveness comes into question
By Sue Rochman
When Katie Couric underwent a colonoscopy on the Today show in March 2000, following the death of her husband from colon cancer, she helped popularize a screening test that many people had avoided because of its strong “ick” factor. She also helped solidify a public health message that most people would distill into something like this: Get screened, have your polyps removed, and wave goodbye to colon cancer.
So it was pretty surprising when colorectal cancer experts found themselves answering questions about two recent research studies that suggested colonoscopy wasn’t as effective as most people believed. The studies differed in their design and approach, and each brought out skeptics and critics. But both led to the same conclusion: The colonoscopy mantra—“colonoscopy = no colon cancer”—was more solid than the data behind it.
The first study to make headlines was published March 5, 2008, in the Journal of the American Medical Association. It suggested that American doctors need to be trained to find flat or concave lesions because they are not only more common in the United States than previously believed, but they are five times as likely as protruding polyps to be cancerous.
The second study, published Jan. 6, 2009, in the Annals of Internal Medicine, caused even more jaws to drop. This case-control study suggested that colonoscopy reduces by only 60 percent to 70 percent a person’s risk of dying of left-sided colon cancers—those in the part of the colon that is within the left half of the abdomen and closest to the rectum. More startling, the research indicated that colonoscopy may fail to prevent any deaths from colon cancers that develop in the right side of the colon.
Cancer specialists have had more time to mull over the first study’s findings, and it’s now clear that not everyone is convinced that flat polyps are as great a problem as the study suggested, because it is still unclear how common they are in the U.S. or how they become cancerous. As Michael LeFevre, a physician who serves on the U.S. Preventive Services Task Force, which develops cancer screening guidelines, puts it, “The question of flat polyps is science in evolution.”
The second study still has people scratching their heads. Gastroenterologists say they have long known that colonoscopy misses some polyps and is not as perfect as many people believed. However, they didn’t expect the effectiveness to be as low as this study suggests.
But Kate Murphy, a colon cancer survivor who serves as the director of research communications for the Colorectal Cancer Coalition, a nonprofit advocacy organization, says that the study’s findings have to be viewed within the context of its design. “It was a retrospective study,” she explains, and “the researchers didn’t have information about how many times the doctors reached the cecum, which marks the top of the colon.” Getting to the cecum is one indicator of a well-done exam.