Purpose: The value of routine colonoscopy in the prevention or early detection of metachronous carcinoma of the colon and rectum remains unproven. This study attempts to clarify this issue.
Methods: An analysis of a personal series of 460 patients with primary colorectal carcinoma treated by the second author between 1972 and 1990 was reviewed. After various exclusions, there remained 231 patients who had been prospectively followed by colonoscopy with a mean follow-up period of 5.6 years.
Results: In 48 (21 percent) patients, there were synchronous adenomas present at the time of the initial resection for carcinoma and 35 (73 percent) of these patients subsequently developed metachronous adenomas, being recurrent in 22. Ninety-five (52 percent) of the 183 patients without synchronous adenomas eventually developed metachronous adenomas, so that overall 130 (56 percent) patients developed a metachronous adenomas. Four patients developed a metachronous carcinoma that was either Dukes A or B, and all remain well at the time of final follow-up. These metachronous carcinomas were found after a mean interval of seven and three-quarter years. All four patients had synchronous adenomas and all developed metachronous adenomas on multiple occasions before the metachronous carcinoma was detected. Thus, a subset consisting of only 22 patients produced all four metachronous malignancies--a rate of 18 percent.
Conclusion: It would appear that the presence of synchronous adenomas with the subsequent development of recurring metachronous adenomas is significant and warrants a more intensive follow-up program to ensure the early diagnosis and more likely cure of any metachronous carcinoma.