2-YEAR INCIDENCE OF COLON ADENOMAS DEVELOPING AFTER TANDEM COLONOSCOPY

Objectives: We attempted to determine an accurate frequency of new pol yp growth in a cohort of veteran male patients who were initially clea red of polyps by tandem colonoscopy. Methods: Followup colonoscopy was performed 2 yr after tandem colonoscopy. A polyp was categorized as ' 'new'' if it was not located in a segment of the colon or rectum that had harbored a neoplastic polyp of the same histology at tandem colono scopy, in contradistinction to lesions designated as ''same-segment'' polyps. Results: Fifty-eight of 90 patients who had tandem colonoscopy as a part of a previous study were available for follow-up colonoscop y for 2 yr. Ninety-one percent had a history of benign neoplastic poly ps or cancer. Neoplastic polyps were documented in 52% (95% CI, 45-74% ) of patients at followup, and 38% (95% CI, 26-52%) were found to have a total of 31 ''new'' lesions. All new lesions were tubular adenomas. The largest number of new polyps in an individual patient was four, a nd the largest new lesion was 20 mm in size with a flat, linear config uration. Most (25/31) new polyps were less than or equal to 5 min, and the number of neoplastic polyps per patient at follow-up was less tha n at tandem colonoscopy. Conclusions: Approximately one-half of older, male patients with a history of neoplastic polyps will demonstrate ne oplastic polyps at 2 yr. In at least one-third of patients, these appe ar to be new lesions. In some patients, de novo neoplastic polyps can grow to greater than or equal to 1 cm within 2 yr.