{'fraction_non_alphanumeric': 0.017659137577002052, 'fraction_numerical': 0.01190965092402464, 'mean_word_length': 5.074812967581047, 'pattern_counts': {'":': 0, '<': 0, '<?xml version=': 0, '>': 0, 'https://': 0, 'lorem ipsum': 0, 'www.': 0, 'xml': 0}, 'pii_count': 0, 'substrings_counts': 0, 'word_list_counts': {'cursed_substrings.json': 0, 'profanity_word_list.json': 0, 'sexual_word_list.json': 0, 'zh_pornsignals.json': 0}}
Follow‐up surveillance in patients with adenomas

The preliminary experiences of prospective randomized follow-up studies are now available from the National Polyp Study in the United States (including seven centres and nearly 1500 patients with adenomas), and from a Danish centre study with more than 800 patients.'-3 Both studies are designed to show possible differences in cost-effectiveness and cost-benefit between different frequencies of follow up examinations, but both may also give some information about the risk of colorectal cancer in these patients compared with the normal population. Length of follow up varies from 3 to 10 years. No previous diagnosis of colorectal adenoma or cancer, and complete colonoscopy are necessary for entry in the studies. The American study includes comparisons of faecal occult blood tests, colonoscopy and double contrast barium enema. The Danish study includes repeated endoscopic surveillance of the initial polyp site within 3 months in patients who had had piecemeal polypectomy , and colonoscopy within 3 months in those with multiple polyps. Intervals between follow-up examinations vary from 6 months to 4 years in the two studies. The terminologies of pathology in the two studies are similar and follow the recommendations proposed by a working team report from the IV European Congress of Digestive Endoscopy in 1988.4 Both studies have revealed a significant number of adenomas at follow-up examination. More new adenomas are detected in patients having two examinations within 3-4 years than in those having no more than one examination. The Danish study has shown a 50% risk of new adenomas within 10 years (Fig. 1). Adenomas found at follow-up examination are small, mainly tubular and more evenly distributed than the original adenomas and rarely have severe dysplasia (Table 1). Multivariate analysis suggests that more adenomas are found at follow-up examination in patients who have large villous adenomas or multiple adenomas at their initial examination. The value of prognostic factors is not clear because of the unimportant pathology found at follow-up examinations. So far it has not been possible to discover whether followup programmes influence the risk of developing cancer and it must be kept in mind that colonoscopy with polypectomy is not without risk to the patient, making it desirable to prolong the intervals between re-examinations. The interim 1 VI