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Am Fam Physician. 2002;66(8):1548-1549

Major guidelines regarding colon cancer screening suggest beginning such testing at 50 years of age in patients at average risk. Imperiale and colleagues detailed the results of a large screening trial of colonoscopy for cancer and polyps among patients who were 40 to 49 years of age, who would not be offered screening according to present guidelines.

The investigators analyzed data from a patient population that received colonoscopy screening as an employee benefit for all persons who were at least 40 years of age. All patients were asymptomatic for any bowel disease and had no personal history of colorectal cancer, colorectal polyps, or inflammatory bowel disease. Of the 3,421 employees screened by colonoscopy, 906 were 40 to 49 years of age. Male subjects comprised 61 percent of participants.

Nearly 90 percent of screened patients who were 40 to 49 years of age had either no polyps or only hyperplastic polyps. Advanced neoplasia was defined as a tubular adenoma at least 1 cm in diameter, any polyp with villous features, any tissue with high-grade dysplasia, or a cancer. Advanced lesions were found in 3.5 percent of patients. If tubular adenomas at least 1 cm in diameter were not considered an advanced lesion, the rate decreased to 2.3 percent. No cancerous lesion was detected in the entire cohort of 40- to 49-year-old subjects. By comparison, advanced neoplasia rates were 4.1 percent in the 50- to 59-year-old group, 7.8 percent in the 60- to 69-year-old group, and 11.8 percent in patients who were at least 70 years of age.

The authors concluded there was a “low yield” to screening colonoscopy in patients 40 to 49 years of age, which supported the recommendation from current guidelines to start screening at 50 years of age and beyond.

editor's note: Studies with so-called “negative” results, where the suggested intervention or treatment does not improve outcomes, rarely get much attention in the lay press or medical literature. While previous results from Imperiale's investigative group have generated some controversy for appearing to promote screening colonoscopy over sigmoidoscopy, one has to respect the scientific discipline it required from the authors and the journal to promulgate the results of this analysis, where not a single cancer was found among the 906 persons screened.—b.z.

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