Roel Bogie

General discussion

requiring expertise and time. 29 Furthermore, the risk of perforation and bleeding is higher with ESD than EMR. 30 Finally, ESD only leads to curative resections of superficial neoplasia, and in case of submucosal invasion, only T1a lesions can be curatively treated by ESD. 31 On the other hand, in case en-bloc resection is needed, ESD is less invasive with lesser side effects compared to surgical resection. So, when en-bloc resection is indicated, ESD is an attractive therapeutic option for superficial neoplasms. Which colorectal neoplasms should be resected en-bloc is still under debate. In Japan, ESD is widely availablewith high level expertise and facilities. 29 Therefore, in Japanmany LSTs are treated by ESD. In theWesternworld, however, only few centers performESD and the need for en-bloc resection is still questioned. 32, 33 En-bloc resection reduces the risk of recurrence, 34-36 but most recurrences can be treated with conventional endoscopic resection afterwards. 37 A meta-analysis on LST treatment reports that 87.7% of all LST recurrences could be effectively treated by colonoscopy. 38 When submucosal invasion is suspected, en-bloc resection facilitates histological diagnosis and is able to provide information about multifocal invasion. 6 With respect to LSTs, the largest risk on submucosal invasion and multifocal invasion exists in LST-NG-PD. 10, 18, 39 LST-G-NM may also contain multifocal invasion, 10, 18 but till now piecemeal EMR with resection of the dominant nodule in one piece and then removal of the granular ‘skirt’has been considered as effective treatment. 6, 29, 32, 39 Recently, data of LST-G-NM showed that the risk of submucosal invasion is highly dependent on colonic location. Rectal LST-G-NM have a higher risk on submucosal invasion than LST-G-NM located elsewhere, especially with increasing size, justifying en-bloc instead of piecemeal resection. 17 Compared to completely flat lesions, in colorectal neoplasms with large nodules, endoscopic clues pointing to the presence of submucosal invasion are not present or when present, are often missed. 19 In the near future, ESD procedures will be more widely applied inWestern countries. In doing so, evidence will become available on cost-effectiveness of more invasive endoscopic treatments for high risk LSTs. 40, 41 EMR was used as technique for endoscopic resection of LSTs described in Chapter 4 . An overall residue/recurrence risk of 14.2% was found. This rate is in line with the 12.6% recurrence rate found in a meta-analysis. 38 ESD was not available in the period when the data were collected. Nonetheless, with increasing skills and experience still more than half of all LSTs were resected en-bloc in the final year of study. The quality of endoscopic resection after the start of the national CRC screening program was studied in Chapter 5 . In this study, national screening data of the first three years of the program was used, supplemented by detailed outcome data of the first one and a half year collected in a regional cohort. This study showed that even after the start of the national CRC screening program in 2014, most LNPCPs (including large LSTs) were still resected by EMR. Only 1% was resected by ESD. As expected, recurrence rates were higher with piecemeal resection (22% in piecemeal resected and 8% in en-bloc resected LNPCPs) and this percentage increased with larger size. Still, the clinical success rate, defined as no residual or recurrent tissue at 12 months after first encounter, was 87% overall (95% CI: 80 – 92). Chapter 5 concluded that the resection quality of LNPCPs within the national screening program should improve, perhaps with additional training or centralization. Within piecemeal resected LNPCPs by EMR, factors as size ≥40mm, intraprocedural bleeding, and high-grade dysplasia are predictive for recurrence, stressing the need for well-timed second look colonoscopy. 42 Options to reduce the high recurrence rates after piecemeal resection were studied in Chapter 6 . Thermal ablation of resection margins is a technique applied after full macroscopic resection of neoplasms. With the idea that microscopic remnant neoplastic tissue remains in the

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