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 of the Indiana University, Indianapolis, and his associates.
The investigators determined the incidences of any neoplasia and of advanced neoplasia at 5-year rescreening colonoscopy in a population of 1,256 middle-age people at average risk for colorectal cancer. The study subjects had undergone initial screening colonoscopy with 36 gastroenterologists at seven clinical centers in Indiana between 1995 and 2000. A total of 1,057 subjects had no polyps, and 199 had only hyperplastic polyps at that time.
Five years later, they underwent follow-up colonoscopy at a mean age of 57 years. No cancers were discovered.
However, 201 subjects (16%) had neoplastic polyps at rescreening. Sixteen subjects (1.3%) had advanced neoplasms at rescreening. These results are similar to those of previous studies of interval rescreening among people with normal findings on baseline colonoscopy (N. Engl. J. Med. 2008;359:1218-24).
In an editorial comment, 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,” Dr. Fletcher said (N. Engl. J. Med. 2008;359:1285-7).
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.