Watchful waiting versus colorectal resection after polypectomy for malignant colorectal polyps.

INTRODUCTION: Unexpected malignancy in removed colorectal polyps is reported in up to 9% of cases. The introduction of screening for colorectal cancer will inevitably increase the number of removed colorectal polyps and therefore also the incidence of malignant polyps. The treatment strategy is either watchful waiting or subsequent colorectal resection. The aim of this study was to perform a preliminary evaluation of the oncological results of polypectomy for malignant polyps with or without subsequent resection, including the patients' long-term survival. METHODS: This was a retrospective analysis of prospectively collected data on 50 patients with unexpected malignancy after a polypectomy treated between January 2003 and January 2008. A total of 27 patients (54%) were treated with watchful waiting, and 23 (46%) underwent subsequent surgery. The Mann-Whitney U-test and chi-square test were used to compare the results between the two groups. RESULTS: There were more patients in the surgery group with positive resection margins after the polypectomy (p = 0.002). No difference was found regarding tumour differentiation grade, lymphovascular invasion, local recurrence or distant metastasis. Intraoperative complications occurred in three patients (13%, 95% confidence interval: 0-28%). In all, 16 of the 23 operated patients had no residual tumour. Overall long-term survival was higher among the operated patients (p = 0.005), but there was no difference in cancer-free survival (p = 0.071). CONCLUSION: Overtreatment of patients with malignant colorectal polyps seems to occur. Which patients benefit from further surgery has yet to be determined. FUNDING: not relevant. TRIAL REGISTRATION: not relevant.