For patients at average risk for colorectal cancer whose initial screening colonoscopy reveals no abnormalities, an interval of 5 years or longer before the next exam appears to be safe.
The 5-year risk of colorectal cancer in such patients is extremely low, and the risk of advanced neoplasms also is low—findings that “provide support for rescreening after an interval of 5 years or longer,” said Dr. Thomas F. Imperiale, professor of medicine, Indiana University, Indianapolis, and his associates.
They studied 1,256 middle-aged people at average risk for colorectal cancer who had undergone initial screening colonoscopy with 36 gastroenterologists in Indiana between 1995 and 2000. A total of 1,057 subjects had no polyps, and 199 had only hyperplastic polyps at that time.
No cancers were discovered 5 years later at follow-up colonoscopy at a mean age of 57 years. But 201 subjects (16%) had neoplastic polyps at rescreening, including 16 (1.3%) with advanced neoplasms. These results are similar to those of previous studies of rescreening among people with normal findings on baseline colonoscopy, the researchers said (N. Engl. J. Med. 2008;359:1218–24).
In an editorial, Dr. Robert H. Fletcher, professor emeritus at Harvard Medical School, Boston, said that even though intervals of 5–10 years between screenings have been recommended, “in clinical practice, intervals between colonoscopic examinations have apparently not reflected the evidence. In a survey, endoscopists in the United States said they performed follow-up colonoscopies at substantially shorter intervals than those recommended by expert groups. Perhaps with stronger evidence that longer intervals are safe, practicing endoscopists will be persuaded to extend the time between colonoscopic examinations,” Dr. Fletcher said (N. Engl. J. Med. 2008;359:1285–7).
Dr. Imperiale's study involved employees, retirees, and dependents of Eli Lilly & Co. The study was supported by a grant from the National Institute of Diabetes and Digestive and Kidney Diseases, and no potential conflict of interest was noted. Dr. Fletcher reports serving as a paid consultant for Exact Sciences.