The Incidence of and Risk Factors for Local Recurrence With Malignancy After Endoscopic Resection of Large Colon Polyps With High Grade Dysplasia

Abstract

Introduction: In western countries, most benign large colonic polyps (LCP) are removed by piecemeal endoscopic resection. This technique has gained widespread acceptance as most recurrences are believed to be local, benign and amenable to further endoscopic management. Malignancy at the resection site of benign polyps with high grade dysplasia (HGD), has been described in Asian literature, and is of concern. We evaluated the incidence of local invasive colorectal carcinoma (CRC) at prior polypectomy site of LCP with HGD, and the associated risk factors. Methods: This retrospective study identified consecutive patients undergoing complete endoscopic resection of LCP >= 20 mm with HGD, at a single large Western center between January 2000 and December 2016. Demographic, clinical, endoscopic and pathologic data were abstracted from the patients’ index procedure. Follow up data to identify recurrent disease were collected from all subsequent endoscopic and surgical procedures, radiologic imaging, and pathology. Exclusion criteria included a grossly incomplete initial resection, polyposis syndromes and personal history of colon cancer. Results: A total of 254 LCP with HGD were resected in 229 patients. Median polyp size was 29.2 mm (range: 20 -100 mm). 138 lesions were resected in piecemeal fashion and 116 en-bloc. Cancer was diagnosed at the site of polypectomy on follow-up in six cases. Of these cases, three cases were diagnosed at early stage (stage I or II), and three cases were diagnosed at advanced stage (stage III or IV) (Table 1). Median time to cancer diagnosis was 28.5 months. Distant metastatic disease was found at time of the diagnosis in two cases. Based on time-to-event analysis, the estimated incidence of cancer related to the index polyp was 1.3% at 1 year and 4.5% at 5 years (Figure 1). Table 2 presents the analysis of risk factors for the local recurrence with malignancy. Although not statistically significant, all malignant cases occurred after piecemeal resection and none after en-bloc resection (HR, 11.4; 95% CI, 0.48-273.0, p = 0.13)113_A Figure 1. The cumulative incidence of invasive malignancy by resection method and size of lesionConclusion: Malignancy after endoscopic resection of LCP with HGD is uncommon but if diagnosis is delayed it can be lethal. Close endoscopic surveillance is crucial and when possible en-bloc ESD resection, which is associated with lower recurrence rates, should be considered for LCP with HGD113_B Figure 2. Characteristics of Local Recurrence with Invasive Malignancy113_C Figure 3. Analysis of Factors for Local Recurrence with Malignancy: Unadjusted Marginal Cox Regression Analysis