The Australian Colonic Large Sessile Lesion Endoscopic Resection Study (ACE)

Description

Colonoscopic polypectomy is well established as an effective way of reducing colorectal cancer mortality. The majority of polyps detected and removed at colonoscopy are adenomas <10mm in size without advanced histology. These lesions have a low risk of progression to malignancy and are relatively easily removed by standard snare polypectomy with low complication rates. Polyps that are sessile or flat and greater than 20mm in size are found in approximately 1% of all colonoscopies and are more difficult to manage. These lesions, known as large sessile lesions (LSL), have a high rate of advanced histology. Traditionally they have been managed by referral for open or laparoscopic surgery, which is definitive, but invasive, costly and associated with a significant mortality risk in patients with advanced age or comorbidities5. Endoscopic Mucosal Resection (EMR) has emerged in recent years as an alternative to surgery that is now becoming the standard of care. It is an outpatient procedure which is effective, safe and less costly than surgery when delivered at a tertiary referral centre6.

The Australian Colonic Endoscopic Mucosal Resection study (ACE), comprises two multicentre prospective observational studies which examined EMR of colonic LSL (Ethics approval No.s HREC JH/TG 2008/9/6.1(2858) and HREC/13/WMEAD/233 (3778)). The project now has an extensive dataset from leading colonic endoscopic resection centres in Australia on more than 2000 lesions resected over 4 years since September 2008.

These studies have been successful in addressing several aspects of the resection of LSL, resulting in several high profile papers in internationally recognised journals. The collection of this data has produced robust information on the efficacy of the procedure4, recurrence rates, bleeding complications and mortality and costs when compared to surgery. Single centre analysis of the ACE dataset at Westmead has also allowed insights into how to refine the procedure to improve outcomes. The target sign is now a recognised indication for the placement of clips to prevent perforation, CO2 insufflation for EMR has been shown to be superior to air insufflation and succinylated gelatin (Gelofusine) has been shown to be superior to normal saline as a submucosal lifting agent. Assessment and management strategies for bleeding and deep mural injury or perforation have been derived from analysis of the data. Snare tip soft coagulation of the resection margin post-EMR has been shown to reduce recurrence in a randomised controlled trial. Several ACE study papers have been incorporated into review papers and international guidelines for the safe and effective performance of EMR.

There remain a number of unanswered questions regarding the endoscopic resection of large sessile lesions and a new study incorporating a greater number of endoscopy units around Australia will allow these to be addressed as well as answer questions on the clinical effectiveness of the technique. Enhancing the prediction of submucosal invasive cancer, advanced lesion classification, validation of the assessment of deep injury, treatment of lesion margins post resection to reduce recurrence, prevention and prophylaxis of bleeding, and subtype analyses of the different histological groups of colonic lesions will be examined.

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