Cold Snare Polypectomy Versus Endoscopic Mucosal Resection for Colonic Sessile Serrated Polyps - A Randomised Controlled Trial

Colorectal cancer (CRC) is the third most common cancer and it remains the second most commonly diagnosed malignancy in Australia. Colonoscopic polypectomy reduces the incidence and mortality from CRC by disrupting the adenoma-carcinoma sequence. Screening for CRC has proven to be effective in reducing mortality and morbidity from CRC and has become common practice. Interval cancers (development of a CRC within 6 to 60 months of a colonoscopy) occur in 6% of patients and estimations showed that up to 27% of these are due to incomplete adenoma resection.

The serrated neoplasia pathway accounts for 20- 30% of sporadic cancers. Serrated precursor lesions are thought to be a major contributor to the relative failure of colonoscopy in the prevention of proximal colorectal cancer (CRC) and to the 5- 7% of CRCs which occur in the period after complete colonoscopy and prior to surveillance, termed 'interval' cancer.

In addition to being difficult to detect, sessile serrated polyps (SSPs) are more likely to be incompletely resected than conventional adenomas. The CARE study demonstrated that 31% of SSPs had remnant tissue in the resection defect compared with 7.2% of conventional adenomas, and in lesions greater than 10 mm in size, residual tissue remained in 47.5%. SSPs may have indistinct margins, and smaller lesions may prove difficult to entrap with the snare because of their flat nature. SSPs also may contain dysplastic foci within the lesion, with an endoscopic appearance indistinguishable from conventional adenomas, and the surrounding serrated component may be overlooked and incompletely resected if this is not recognized.

The technique of colonoscopic polypectomy is continually evolving, leading to better outcomes with regard to polyp detection rate, complete resection rate (CRR) of polyps, patient comfort, safety and cost-efficacy. Although colonoscopy is considered the 'gold standard' for detecting and removing polyps, the technique is still imperfect. Questions about best practice for polypectomy remain, so optimizing the technique is expected to lead to better patient outcomes. The optimal treatment of SSPs should be effective, safe and inexpensive.

Such lesions can be removed by cold snare polypectomy or by endoscopic mucosal resection. Cold snare polypectomy (CSP) is now common practice and has proven to be a safe and effective technique for removal of any small polyps (<10 mm). Because of their physical characteristics, use of thin wire snares leads to a fast tissue transection and ability to remove SSP relatively swiftly. The size of snares suitable for SSP CSP is approximately 9 mm. Thus lesions greater than this size would need to be removed in more than one piece, introducing the possibility of incomplete resection. Endoscopic mucosal resection (EMR) is well established for laterally spreading colorectal lesions. It involves submucosal injection and diathermy assisted snare resection by piecemeal or en-bloc depending on polyp size. En bloc resection is possible for lesions up to 20 mm and facilitates histopathological evaluation. EMR is more time consuming than CSP and may be associated with diathermy related complications such as postpolypectomy bleeding, perforation and pain. The most efficient and safe method of removal of SSP has not been established.