Roel Bogie

Endoscopic subtypes of colorectal laterally spreading tumors and risk of submucosal invasion: A meta-analysis

Introduction Large flat-appearing neoplasms, also known as laterally spreading tumors (LSTs) 1 constitute an important contributor to post-colonoscopy colorectal cancer. 2 Endoscopic diagnosis and resection of LSTs is known to be technically difficult. 3, 4 The European Society of Gastrointestinal Endoscopy (ESGE) guidelines on colorectal polypectomy and the British Society of Gastroenterology guidelines for the management of large non-pedunculated colorectal neoplasms state that most colorectal neoplasms can be treated with (piecemeal) endoscopic mucosal resection (EMR). 5, 6 Endoscopic resection should be safe and performedwith aminimumnumber of pieces. If superficial submucosal invasion (SMI) is suspected, en-bloc resection should be the therapy of choice. En-bloc resection for superficial neoplasms larger than 20mm can be achieved by endoscopic submucosal dissection (ESD). 7 The most effective LST treatment strategy is still under debate. An Australian multicenter study showed that piecemeal EMR is an effective treatment in most cases of flat and sessile neoplasms ≥20mm. 8 After initially successful EMR, 98.1% of the patients were free of adenoma and did not require surgery. A Japanese study from a centre experienced in ESD showed that granular LSTs with a dominant nodule and non-granular LSTs with a pseudo-depression are associated with a substantial risk of SMI (19 and 39% respectively) which was multifocal in 16 and 45%, respectively. This group suggested that en-bloc endoscopic resection is the preferred therapy in such cases. 9 Although clinical practice guidelines acknowledge substantial differences in the risk of SMI between different LST subtypes, the therapeutic implications are unclear. A large number of studies have examined the risk of LSTs containing SMI, but no meta-analysis of the data is currently available.We performed a systematic reviewwithmeta-analysis to determine endoscopic predictors of increased risk of SMI in LSTs in order to provide a more solid basis for evidence-based therapy. Methods We conducted and reported this systematic review according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) recommendations. 10 We employed an a priori established protocol 11 which is available on request. Definitions The term ‘laterally spreading tumor’ defines a laterally growing superficial neoplasm (instead of upward or downward growth) of at least 10mm in size. 1 The term ‘superficial neoplasm’ relies on macroscopic assessment and refers to lesions that are non-invasive in appearance. 12 Superficial neoplasms can contain low grade dysplasia, high grade dysplasia (HGD) or submucosal invasion (SMI) which are amenable to endoscopic resection. The term ‘non-polypoid’ is defined as a lesion with a height less than half of its diameter 13 or as a lesion with protrusion <2.5mm above the mucosa. 14, 15 We used the WHO classification for histopathology. 16 Intramucosal carcinoma was coded as adenomatous HGD. LSTs were subclassified using the endoscopic Kudo classification (which should not be confusedwith the Kudo pit-pattern classification) into LST-granular (LST-G), which comprises the homogeneous (LST-G-H) and nodular mixed (LST-G-NM) subtypes, and LST-non-granular (LST NG), which comprises the flat elevated (LST-NG-FE) and pseudo-depressed (LST-NG-PD) subtypes

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