Roel Bogie

General introduction

Aims and outline of this thesis In this thesis, we hypothesized that LSTs are an important contributor to PCCRCs. A number of studies were conducted on both topics, each also individually important for quality of colonoscopy. The aims of this thesis are (I) to investigate the malignant potential, clinical significance, and therapeutic options of LSTs, (II) to examine how to limit the risk of PCCRCs and (III) to study whether non-polypoid and specifically LSTs are major contributors to PCCRCs. The first part of this thesis is about LSTs (in combination with LNPCPs) and their clinical significance ( Chapters 2-6 ). Chapter 2 focuses on the LST definition and whether it is applicable in clinical practice. In this study the endoscopic Kudo LST classification is validated among international experts and endoscopy trainees. In Chapter 3 we aimed to investigate worldwide prevalence and malignant potential of LSTs. In Chapter 4 we focused at the LSTs diagnosed in the Maastricht University Medical Center and we investigated whether patients with LSTs have a different risk of colorectal neoplasia than other patients with colorectal neoplasms. Whether prevalence of LSTs (and the other LNPCPs) increased in national CRC screening setting and the management of these lesions is studied in Chapter 5 . In Chapter 6 we performed another meta-analysis to see whether thermal ablation could contribute to a more effective resection of LNPCPs (including LSTs). PCCRC is the subject of the second part of this thesis ( Chapter 7-11 ). PCCRCs are important regarding effectiveness and safety of colonoscopy, especially with the implementation of national colorectal cancer screening programs. In Chapter 7 we summarized Western post-colonoscopy surveillance guidelines and added practical tips and tricks to optimize surveillance to prevent PCCRCs. Currently surveillance intervals are calculated based on polyp numbers and polyp size and histology. For histology, resection and pathological examination is necessary for each polyp. Whether we are ready for optical diagnosis only in small polyps and calculate surveillance intervals based on this assessment, was studied in Chapter 8 . As we hypothesize that non-polypoid colorectal neoplasms (NP-CRNs) are important contributors to PCCRC, training in the detection and resection of NP-CRNs may reduce PCCRC incidence. This was studied in Chapter 9 . Because of the higher prevalence NP-CRNs, the risk of developing a PCCRC may also been increased. Further investigation into the role of NP-CRNs in the development of PCCRCs was done in Chapter 10 . The biology of PCCRCs development was studied in this chapter by using molecular analysis. A molecular analysis of PCCRCs was performed and the profiles found were compared with the known profile of detected (previously called ‘prevalent’) CRCs. In Chapter 11 the incidence of PCCRCs among inflammatory bowel disease (IBD) patients was studied. Patients with IBD have relatively more often NP-CRNs than the general colonoscopy population, i.e. patients referred for screening colonoscopy or patients with symptoms justifying colonoscopic examination. Finally, in Chapter 12 we summarize these findings and discuss the current insights, implications for clinical practice and remaining questions about LSTs, PCCRCs and their connection.

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