Transanal Endoscopic Microsurgery Versus Endoscopic Submucosal Dissection For Large Rectal Adenomas

PROBLEM DEFINITION Rectal cancer is a common disease in Western countries, increased with high age, male sex and obesity (1,2). As for other districts, premalignant intraepithelial neoplasia inside a rectal adenoma precedes the occurrence of invasive rectal cancer (3,4). Early endoscopic detection and removal of rectal adenomas prevents the development of rectal cancer and is therefore the most reliable contributor to the 'cure' of this disease (5,6). When rectal adenomas become large, however, standard endoscopic therapies like loop polypectomy or one-step endoscopic resection result inadequate. Therefore, large rectal adenomas must be removed en-bloc either surgically or by extended endoscopic submucosal dissection (ESD).

In 1983 a novel surgical approach for the resection of large rectal adenomas has been introduced in the clinical practice in Germany: Transanal Endoscopic Microsurgery (TEM).(7) This procedure encompasses general anesthesia and the use of expensive specialized equipment. On the other hand, it generally allows a full-thickness rectal wall excision. Since its introduction, many surgical practices have adopted TEM as the new standard therapy for large rectal adenomas (8). In more recent years advanced endoscopic therapies like extended ESD have rapidly evolved.(9).

For extended ESD an en-bloc specimen, including mucosa and consistent portion of the submucosal layer, are resected instead of the full-thickness rectal wall, combining the advantages of an en-bloc resection with potential benefit of fewer complications.

Supporters of the TEM technique praise the excellent exposure of the rectum and the minimal invasiveness, as opposed to conventional surgical techniques.(10-12) Besides, recurrence rates after TEM appear to be lower when compared to conventional surgical transanal excision.(13) The TEM technique has shown to be highly efficacious in several retrospective and prospective case series with reported recurrence rates of 0-19% and complication rates of 2-21%.(14-23) On the other hand, extended ESD has gained more and more support in the last few years, mainly due to good clinical results after ESD of neoplasia in the esophagus and stomach as reported in Japanese centers (24,25) ESD has also been described for the treatment of large colorectal adenomas, revealing recurrence rates of 0-9% and complication rates of only 0-9% (9,27). If adenomas could not be removed completely during one ESD attempt, repeat ESD for residual disease generally led to an overall success rate of 96-100%. In general, all recurrences were detected during the first control endoscopy after 3 months; repeat endoscopic resection of residual disease led to an overall success rate of almost 100%.

Since the efficacy of extended ESD for large rectal adenomas appears to be comparable to TEM, we decided to design this randomized trial. In fact, until now, TEM and ESD have never been formally compared, and no such comparative studies have been registered at this moment. Although selection bias inevitably exists in prospective and retrospective case series, the results of these studies suggest that both TEM and ESD have comparable recurrence rates. Even when recurrences occur after TEM or ESD, most of these can successfully be re-treated without the need for radical surgery. The literature furthermore suggests that ESD is associated with fewer complications, reduced hospital admission, and no general anesthesia is required for ESD, all of which are favorable in both patients' and societal perspective. These contrasts of the two procedures might well lead to differences in costs and quality of life. Therefore, we designed a multicentre randomized trial to compare TEM and ESD for the resection of large rectal adenomas.