Factors Associated With Margin Positivity and Incidental Carcinoma in Patients Undergoing Transanal Endoscopic Microsurgery (TEMS) for the Management of Adenomatous and Dysplastic Rectal Lesions.

Colorectal cancer screening has resulted in an increased detection of early premalignant rectal lesions. Transanal endoscopic microsurgery (TEMS) is a minimally invasive procedure for the resection of dysplastic and selected early malignant lesions with organ and functional preservation. The aim of this study was to assess factors associated with positive resection margin and the underlying invasive component. This was an analysis of a prospective consecutive series of all TEMS procedures performed over the last 10-year period. Data was collated from hospital databases and operative theater registers. Statistical analysis was performed using Minitab-V18 with a P<0.05 regarded as significant. In total, 328 procedures were performed on 292 patients. The cohort included 165 male patients and 127 female patients with a mean age of 66.3 years (19 to 95 years). A total of 274 procedures performed were en bloc excisions and 54 procedures were piecemeal debulking excisions for larger lesions follow by formal TEMs at an interval. The mean tumor size was 41.9 mm (10 to 150 mm), and the mean distance from anal verge was 9.3 cm (2 to 20 cm). Clear margins were achieved in 85% of cases. An overall 10.6% of patients had pathologic upgrading to invasive disease after TEMS. Lesion volume was found to influence the completeness of excision, and the widest diameter of the lesions was related to the presence of an invasive component on histology (P=0.002, 0.008, respectively). TEMS is a minimally invasive technique for the resection of rectal lesions that are not amenable to endoscopic removal. Lesion size and endoscopic diameter were associated with invasive component and margin positivity, respectively. These factors should be taken into consideration when considering TEMS.