title: Transanal endoscopic microsurgery for rectal cancer: T1 and beyond? An evidence-based review.
abstract: The last three decades have witnessed significant improvements in the diagnosis, staging and treatment of rectal cancer leading to a more tailored approach. One of the most clinically relevant advances in this field is represented by transanal endoscopic microsurgery (TEM). Several studies have investigated its role in the treatment of rectal cancer. However, evidence-based recommendations are limited. The aim of this report is to provide an evidence-based review of current indications, controversies and future perspectives of TEM in the management of rectal cancer.
  
  
  
  A review of the literature has been performed in PubMed/Medline electronic databases and the Cochrane Library. Quality of evidence was evaluated according to the GRADE system.
  
  
  
  TEM allows to perform a more accurate en bloc full-thickness local excision of rectal tumors than transanal excision. TEM alone seems to provide similar oncologic results in selected T1sm1 N0 rectal cancers to those achieved by rectal resection and total mesorectal excision (TME), without impairing anorectal function. The oncologic outcomes of neoadjuvant therapy followed by TEM for selected T2 N0 rectal cancers are promising, but this approach is still under evaluation. A word of caution comes from the increased rate of suture dehiscence and rectal pain after TEM. TEM is a promising tool for the surgical treatment of locally advanced rectal cancer as a platform for transanal TME.
  
  
  
  Selected T1 rectal cancers with favorable features may be effectively treated with TEM without jeopardizing long-term oncologic outcomes. The lack of adequate lymphadenectomy represents the main concern of this approach for the treatment of rectal cancer. Several approaches are under evaluation to overcome this limitation.
authors.affiliation: Department of Surgical Sciences, University of Torino, Corso A. M. Dogliotti, 14, 10126, Turin, Italy. meallaix@gmail.com.
authors.forename: Marco E
authors.initials: ME
authors.lastname: Allaix
authors.affiliation: Department of Surgical Sciences, University of Torino, Corso A. M. Dogliotti, 14, 10126, Turin, Italy.
authors.forename: Alberto
authors.initials: A
authors.lastname: Arezzo
authors.affiliation: Department of Surgical Sciences, University of Torino, Corso A. M. Dogliotti, 14, 10126, Turin, Italy.
authors.forename: Mario
authors.initials: M
authors.lastname: Morino
mesh_terms: D013505:Digestive System Surgical Procedures / Q000379:methods; D019160:Endosonography; D006801:Humans; D008198:Lymph Nodes / Q000000981:diagnostic imaging; D020360:Neoadjuvant Therapy; D009367:Neoplasm Staging; D017410:Practice Guidelines as Topic; D012004:Rectal Neoplasms / Q000473:pathology / Q000601:surgery*; D012007:Rectum / Q000601:surgery*; D000067369:Transanal Endoscopic Microsurgery / Q000379:methods*
keywords: Chemoradiation therapy; Evidence based; Full-thickness excision; Lymph nodes; Natural orifice transluminal endoscopic surgery; Rectal cancer; Total mesorectal excision; Transanal endoscopic microsurgery; Transanal endoscopic operation; Transanal minimally invasive surgery