Conventional Versus Cold Snare Endoscopic Mucosal Resection of Colonic Lateral Spreading Lesions - A Randomised Controlled Trial

Colorectal cancer (CRC) is the third most common malignancy worldwide and the fourth leading cause of cancer related death, with rates being highest in Western countries. Colonoscopy is considered the golden standard in colorectal cancer screening and endoscopic resection of precursor lesions (polyps) has been shown to reduce colorectal cancer death. Polyps extending over 10mm, also referred to as lateral spreading lesions (LSL) if non-pedunculated, more often demonstrate advanced histological features and are considered to be at greater risk for malignant transition as compared to their smaller counterparts. Incomplete endoscopic resection of advanced adenomas may lead to adenoma recurrence and contribute to the development of so called 'interval cancers', which occur during the 6 - 36 month period following complete colonoscopy. Interval cancers account for up to 6% of newly diagnosed CRC cases, highlighting the importance of complete resection.

Endoscopic mucosal resection (EMR) is a well-established inject and resect method for the removal of LSLs using chromo-gelofusin based submucosal lift and subsequent cauterisation assisted snare excision. Lesions up to 25mm in size may be removed enbloc, whereas larger lesions are generally removed in a piecemeal fashion. Contrary to enbloc resection, piecemeal EMR is historically associated with relatively high recurrence rates of 15-20%. A recent four centre trial led by Westmead Hospital published in gastroenterology (impact factor 20.8) has shown that application of snare-tip soft coag (STSC) to the EMR defect margins considerably improves recurrence rates to around 7% in adenomatous LSL. Common complications of EMR such as intra-procedural bleeding (IPB) or clinically significant post-procedural bleeding (CSPB), deep mural injury (DMI) and post-polypectomy coagulation syndrome (PPCS) are largely related to the use of cauterisation for tissue transection. Although complication rates have improved and effects can often be managed endoscopically, further optimization of the EMR safety profile is needed in the background of an aging target population with multiple co-morbidities and widespread use of anticoagulants.

Cold snare polypectomy (CSP) has become the standard of care for removal of subcentimeter polyps. CSP relies on the use of dedicated stiff thin wire snares that are able to swiftly cut through mucosal tissue without the need for cauterisation, leaving intact the muscularis mucosa and the deeper submucosal layers, virtually excluding the risk of perforation. The absence of delayed cauterisation effect significantly reduces the risk of post-polypectomy bleeding, even in patients on anticoagulant therapy. Complete resection rates of polyps ranging from 6 to 10mm in size were found to be non-inferior in CSP as compared to cauterisation based resection. Moreover, resecting a sufficient margin of normal mucosa surrounding the polyp (i.e. >1mm) yields an excellent 98% complete resection rate in polyps <10mm in size without increasing the risk of delayed bleeding. Meta-analysis demonstrated a significantly shorter procedure time when applying the cold snare resection technique in small polyps. Snare size limitations of dedicated cold snares however do not allow for en-bloc resection of polyps >10mm.

Recently, cold snare piecemeal EMR was shown to be safe and effective for the removal of large sessile serrated polyps (SSP). Combined evidence from a limited number of small single centre mostly retrospective studies investigating cold snare piecemeal polypectomy in adenomas over 10mm demonstrated recurrence rates of around 11% whilst maintaining an excellent safety profile with minimal complication rates. However, recurrence rates rise to 22% in the subgroup of polyps over 20mm. Thus far cold snare piecemeal polypectomy of lateral-spreading adenomas has not yet been compared to conventional EMR in prospective randomized fashion.