Roel Bogie

Chapter 1

Colonoscopy is the gold standard method for the detection and resection of colorectal neoplasms (CRNs). The opportunity for direct radical resection of detected CRNs is a major advantage of colonoscopy. By removing precursor lesions of colorectal cancer (CRC), colonoscopy is an important tool in the prevention of CRC. It is regarded as safe 1 and effective in confirming the diagnosis and removing precursor neoplasms. The number of colonoscopies performed has further increased as a consequence of the introduction of national CRC screening programs. 2 Healthy, symptom free persons are now receiving colonoscopies in order to prevent CRC later on in life, emphasizing the need for safety and efficacy of colonoscopic procedures and interventions. The search for precursor lesions that may develop into CRC is key, reassembling the ‘hide and seek game' for the endoscopist. The better the endoscopist performs in this game (higher detection of such precursor lesions), the lower the patients’ risk of developing CRC is. 3 This thesis focuses on how to deal with large colorectal neoplasms and how to prevent the occurrence of CRC after colonoscopy, two important topics within colonoscopy safety and efficacy. In the Netherlands, a nationwide CRC screening program started in 2014 with high yields of CRCs, adenomas and serrated lesions. All Dutch citizens between 55 and 75 years old receive biannually an invitation for a fecal occult blood test (FOBT). In case the FOBT is positive (abnormal), the participant will be referred for a colonoscopy. All colonoscopies are performed by experienced, specially trained and monitored colonoscopists to assure high quality standards. After a negative colonoscopy, patients will re-enter the national screening program after 10 years. 4 The screening program poses a burden on colonoscopy capacity, not only because of a high number of patients referred for colonoscopy, but also because of the treatment of the many CRNs found and the high number of surveillance colonoscopies needed. 5 Small CRNs can be resected during the first colonoscopy in most cases, but large CRNs, especially in the case of multiple large CRNs, often need a second colonoscopy to resect the CRNs completely. Furthermore, large CRNs have higher risk of residual and recurrent neoplastic tissue and need second look colonoscopies. Thus, after complete removal of CRNs, depending on number, size, and histology, surveillance colonoscopies may be necessary. 6 Safety and efficacy of colonoscopy Colonoscopy is a safe procedure with overall very low rates of complications 1 such as bleeding, infection and perforation. The risk of complications significantly increases by performing polypectomies especially for large CRNs. 7 Bleeding occurs in 0.06% (95% CI: 0.02-0.11) of all colonoscopies without polypectomy, but when polypectomy is performed, the risk increases to 0.98% (95% CI: 0.77-1.21). 1 The risk of perforations doubles after polypectomy: 0.04% (95% CI: 0.02 0.08) overall in colonoscopies without polypectomy and 0.08% (95% CI: 0.06-0.10) in colonoscopies with polypectomy. 1 Larger CRNs often need more complex procedures like endoscopic mucosal resection or endoscopic submucosal dissection as endoscopic treatment, thereby even further increasing the risk of post-polypectomy bleeding and perforation. 7, 8 In general, resection of large CRNs is associated with higher risk of complication, is more time consuming, and requires often additional colonoscopies and a shorter post-polypectomy surveillance interval. Colonoscopy National colorectal cancer screening program

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