Surveillance after polyp removal: quality really matters

Patients who have adenomas or serrated polyps removed at colonoscopy are believed to be at increased risk of developing more polyps later in life and, eventually, colorectal cancer (CRC). Thus, colonoscopy surveillance after polyp removal is currently recommended. Identifying risk factors that adequately predict the risk of developing advanced polyps and future CRC after removal of colon polyps is the mainstay of post-polypectomy surveillance.

In this issue of Endoscopy, Larsen et al. present the results of an observational retrospective cohort study conducted in Denmark using nationwide health registries [11]. The aim was to evaluate the risk of CRC and advanced adenomas at surveillance in the Danish fecal immunochemical test (FIT)-based CRC screening program for participants with high and intermediate risk adenomas excised according to the European Guideline from 2012 [22]. Moreover, the authors estimated the risk of CRC for those who would not receive surveillance according to the more recent European Society of Gastrointestinal Endoscopy (ESGE) guideline [33]. The results are somewhat surprising. Initially, 17 936 participants from the screening program with adenomas fulfilling the inclusion criteria and with an indication for post-polypectomy follow-up were included. Of those, 10068 underwent surveillance. The authors found that 88 patients (0.9%) developed CRC at the time of surveillance. The risk of developing CRC was higher at 3 years in the intermediate risk group (≥1 adenoma or sessile serrated lesion [SSL] between 10–19 mm, 3–4 adenomas <20 mm, or any adenoma with villous component or high grade dysplasia) than at 1 year in the high risk group (≥1 adenoma or SSL ≥20 mm, ≥5 adenomas), with a prevalence of 1.11% in the intermediate group and 0.59% in the high risk group at surveillance (relative risk [RR] 0.53; 95%CI 0.34–0.84). In contrast, patients in the high risk group had a 24% higher risk of developing advanced adenoma at surveillance. The secondary aim of the study, which involved a simulation of what would happen if the more recent ESGE guideline criteria [33] were applied in this population, showed that the number of CRCs would be significantly higher, with a proportion of 0.87% in patients who would receive surveillance and 1.69% in patients who would not receive surveillance under the new ESGE guideline (RR 1.94; 95%CI 1.18–3.21).

“Taken together, these results highlight one of the possible reasons that could explain the findings of this study, namely the quality of the baseline colonoscopy.”

There are several points about this study worth discussing. First, the results are somehow contradictory, because people in the intermediate risk group, with smaller and fewer lesions, show a higher risk of developing CRC than those in the high risk group. Timing of the surveillance colonoscopy was different in these groups: 1 year in the high risk group and 3 years in the intermediate risk group. In addition, more advanced adenomas were found in the high risk group. A potential explanation is that these advanced lesions progressed to CRC in the 2-year interval between examinations in both groups. However, this is not supported by current theories on dwell time of polyps [44], unless we believe that an excessive number of advanced lesions were undetected or incompletely resected at baseline colonoscopy. It is important also to remark on the high proportion of CRCs detected at surveillance in these data, which is clearly higher than previously described [55].

Taken together, these results highlight one of the possible reasons that could explain the findings of this study, namely the quality of the baseline colonoscopy. No clear data are provided about the completeness of the colonoscopies or the quality of bowel cleanliness that could explain, in part, the results, although a sensitivity analysis including only those with a code for complete colonoscopy and a clear mucosal view did not change the results. In addition, patients who had polyps resected piecemeal and were checked within 6 months were excluded. Theoretically, with these exclusions, only high quality procedures were included and, therefore, the rate of CRC should be low. Moreover, in this study, only type B post-colonoscopy CRCs (PCCRCs) [66] have been included, so with the addition of symptomatic pre-surveillance true interval CRCs and those detected in the future due to symptoms in people who did not receive surveillance, the rate of PCCRC is very likely to be even higher. The authors do not report the adenoma detection rate (ADR) of the endoscopists who participated in the study, they only indicate that they considered whether regions with an overall high ADR of 55%–57% affected the risk in FIT-positive colonoscopies, which is lower than the high ADR rates described in other studies [77] [88]. The quality of endoscopists participating in this screening program could jeopardize its effectiveness, and more information on the ADRs of participating endoscopists could help in the interpretation of these study findings.

The comparison between people who would and would not receive surveillance following the old European [22] or ESGE [33] guidelines revealed a strange difference in CRC rates. Patients who would not receive surveillance according to ESGE guidelines would only be those with 3–4 adenomas and those with adenomas with a villous component smaller than 10 mm. It is difficult to explain why these initial minor findings would lead to a doubling of the CRC risk. Unfortunately, the authors do not provide an adequate explanation for these findings.

The authors finally conclude that their results could indicate that the first colonoscopy after FIT screening may not sufficiently guide the necessary surveillance or screening strategies because of potentially missed lesions. This is true if the quality of the baseline colonoscopy is questionable. There are three possible conclusions to be drawn from this study. First, these results emphasize the important role of quality metrics for endoscopists performing screening colonoscopies, and, therefore, the establishment and knowledge of these quality metrics must be mandatory. Second, it is extremely important that only certified endoscopists who can demonstrate that they meet the appropriate ADR for FIT-based colonoscopy are able to participate in this modality of CRC screening. Finally, it is also necessary that guidelines for surveillance include these quality metrics of the endoscopists who perform screening colonoscopies in their recommendations. In summary, as with many aspects of daily life, in screening and surveillance colonoscopy, quality really matters.

Publikationsverlauf

Artikel online veröffentlicht:
16. September 2024

• References

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