Optimizing Patient Selection for Surgery Using Pathologic Analysis Following Neoadjuvant Therapy in Locally Advanced Rectal Cancer

Eligible patients will undergo endoscopic submucosal dissection (ESD) or endoscopic intermuscular dissection (EID) after two to eight weeks of nCRT completion, depending on the used neo-adjuvant regimen. Procedures will be performed using the GIF EZ-1500 endoscope (Olympus America, Center Valley, PA, USA) and an electrosurgical unit (VIO 300 D; Erbe, Germany) to power the electrosurgical knife (1.5-mm DualKnife J, Olympus America). For mucosal incision, Endocut or Drycut mode will be used, while Precise, Swift or Spray Coagulation modes will support submucosal dissection and hemostasis. An initial submucosal lift will be created by Glycéol Gel injection. The ERBE Flushing Pump (Erbe, Germany) will supply further submucosal lift during dissection through foot pedal-controlled, pressurized injections of methylene blue and saline solution delivered via the DualKnife J's ceramic-tipped tubing.

Close follow-up and endoscopic re-evaluation four to eight weeks after the initial evaluation\*. \*Defined as the first endoscopic evaluation after completion of the neoadjuvant treatment

This technique consists of the surgical complete removal of the rectum, together with the surrounding mesorectum lymphovascular fatty tissue (mesorectum).