Roel Bogie

Chapter 12

Often proximal location

Often proximal location

Plausible

Di cult endoscopic resection

Probable

Residue/ recurrence

Incomplete resection

Plausible

Subtle appearence

Missed lesions

Probable

Newly developed CRC

Patient at higher risk

More CRNs

Speci c modular pro les

Speci c modular pro les

No evidence found

Plausible

Flat appearance

Often at appearance

Figure 12.1: Links between LSTs and PCCRCs.

Link between LSTs and PCCRCs LSTs have already been introduced in Chapter 1 as potential precursor lesions of PCCRCs. Using the collected data in this thesis, we can now update the links between LSTs and PCCRC with further evidence ( Figure 12.1 ). As discussed before, the etiology of PCCRC occurence is thought to be multifactorial, with factors determined by endoscopists, patients, precursor lesions and combinations ( Figure 12.2 ). As discussed in Chapter 2 , about half of all LSTs are found in the proximal colon. For PCCRCs this is 60%. 58 In general, both polyps 65 and CRCs 58 are more frequently located in the distal colon. In Chapter 3 we showed that endoscopic resection of LSTs is difficult. When endoscopic resection was considered to be complete, still 14.7% had residue/recurrence. A large meta-analysis provided data of even higher recurrence rates in large non-pedunculated neoplasms. 36 Our results suggest, however, that not only the LSTs themselves pose a risk for PCCRCs. Patients with LSTs have significantly more often advanced metachronous neoplasms than patients with large polypoid neoplasms. So, with currently accepted surveillance intervals applied, LSTs patients may harbor more potential precursor lesions for PCCRC development and thus may have a higher risk of PCCRCs. LSTs of the non-granular subtype, were also the most common advanced neoplasms found during surveillance after two clearing colonoscopies in the Japanese Polyp Study. 46 This indicates that PCCRC may arise from LST-NG. Some LSTs have a more subtle appearance (LST-NG) than others (LST-G-NM) and the risk of missing a LST will therefore differ by subtype. Because of their size (≥10mm) the risk of missing LSTs in a well-prepared colon will be low, but it is conceivable that a non-granular LST can be missed under a layer of feces. LST-NG-PD pose the highest risk for submucosal invasion ( Chapter 2 ) while the ones with submucosal invasion have the smallest size ( Chapter 3 ). So it is plausible that a high risk LST-NG-PD may be missed and will develop into PCCRC. Furthermore, LST patients may sooner develop metachronous neoplasm, possibly leading to newly developed CRCs.

230