A new study in the Feb. 23 issue of the New England Journal of Medicine adds more support to the use of colonoscopy as a universal screening test to detect colon cancer (or its precursor adenomatous polyps), at a point in time where removal and cure is simple and straightforward.
Researchers at the Memorial Sloan-Kettering Cancer Center in New York analyzed the records of over 2,000 patients who had polyps removed via colonoscopy, and found that their death rate was 53 percent lower than would have been expected from a group who had no colonoscopy performed.
Colon cancer is the second most common cause of cancer death in the United States. About 75 percent of these cancers arise from slow growing polyps. Such polyps are very common-seen in about 30 percent of patients by the age of 50. However, 99 percent of polyps do not become malignant. The classic symptoms of such a malignant transformation include rectal bleeding, changes in bowel habits and weight loss.
Unfortunately, by the time these symptoms develop, many cancers have spread beyond the colon, and are no longer curable. Hence, the development of screening tools to identify polyps in their “pre-malignant” phase in order to allow removal and prevention of cancer related death.
Initial screening efforts focused on taking small samples of stool and testing for the microscopic presence of blood. Called “fecal occult blood testing”, this was a standard for many years, and is still acceptable in conjunction with other techniques.
The next step was aided by the development of tools, which allowed physicians to look into the colon and visualize polyps directly (and, at the same time, to “snip them out” through the tube, allowing for excision and cancer prevention). Sigmoidoscopy was the initial test used—here a small flexible tube is inserted in the rectum to allow examination of the lower colon. Needing no anesthesia, this procedure is easy to perform, but only visualizes part of the bowel. Colonoscopy, which does require sedation, allows the whole colon to be examined and is the method recommended by most physicians today. Of recent interest are different techniques in “virtual colonoscopy”, where CT or MRI scans can be used in lieu of an inserted tube. Virtual colonoscopy is not yet recommended for widespread use, but holds great promise for the future.
The most important take home message is that colon cancer is deadly, but identifiable and preventable. Most patients should begin a screening protocol at the age of 50; those at higher risk (African-Americans and those with a family history) should discuss with their family physician the advisability of starting at a younger age.
For more on colon cancer screening, please check out this website.