Three randomized long-term surveillance trials in patients with sporadic colorectal adenomas

Guidelines for surveillance of patients with previous sporadic colorectal adenomas are based on retrospective long-term follow-up and prospective short-term studies. The aim of the present studies was to compare relative risk (RR) of new neoplasia as well as complications, using different intervals between examinations in long-term surveillance.

Between l98l and l991, patients with pedunculated and small, flat and sessile adenomas were allocated at random to a 24 months (group A) or 48 months (group B) interval between surveillance colonoscopies (n=671). Patients with flat and sessile adenomas greater than 5 mm in diameter were randomized to intervals of 6 months (group C) or 12 months (group D) between l981 and 1987 (n=73). Finally, 200 patients with similar adenomas as in groups C and D were randomized to 12 months (group E) or 24 months (group F) from 1988 to 2000. The study ended in 2002.

Advanced adenomas were equally as frequent in group A and group B, but colorectal cancer (CRC) was found significantly more often in group B (RR = 6.2 (1.0-117.4)). Severe complications occurred in 4 patients in group A and 2 patients in group B. Advanced new adenomas tended to be more frequent in group D than in C (p=0.08), but only one CRC was detected and this was in group C. There was no significant difference in the risk of CRC between the E and F groups, but the two cancers in group E were both early stage, in contrast to those in group F. Severe complications were seen in one patient in group E and also in group F.

The results suggest that 2-year intervals should be used between colonoscopies in patients with previous pedunculated adenomas and small, flat and sessile adenomas, whereas larger, flat and sessile adenomas may need intervals of 1 year.