Can a high-quality screening colonoscopy decrease the need for subsequent surveillance colonoscopies?

Colorectal cancer (CRC) is the third most common cancer worldwide, with 2 million new cases diagnosed in 2020 and approximately one million deaths yearly [1]. Moreover, the International Agency for Research on Cancer estimates that by 2040, the global burden of CRC will have increased by 56 %, reaching 3 million new cases per year [1]. Screening and surveillance colonoscopies, which allow for polyp detection and removal, are critical in lowering CRC incidence. However, surveillance examinations account for up to 40 % of all colonoscopies, and incorrect surveillance accounts for one-third of the workload in CRC screening programs [2] [3]. As a result, updated surveillance recommendations that optimize colonoscopy services without harming patients should be considered. Although the ideal strategy is currently unknown, ongoing investigations are evaluating potential criteria to determine which patients benefit the most from surveillance and the appropriate time frame between subsequent colonoscopies [4].

In this issue of Endoscopy, we follow with great interest a retrospective national cohort study from Bonnington et al. [5]. The authors aimed to delineate the aforementioned criteria, by: 1) determining the surveillance yield for CRC and advanced adenoma; 2) identifying the possible predictors for surveillance outcome; and 3) comparing surveillance cohorts with the general population in terms of CRC rates.

“... individuals with a single adenoma ≥ 10 mm had a low likelihood of having additional adenomas found on surveillance follow-up (6.1 %). Hence, it is possible that this group could avoid surveillance by colonoscopy, especially as it represents almost one-third of all surveillance cases.”

In total, 44 151 individuals from the English Bowel Cancer Screening Programme underwent post-polypectomy surveillance between 2006 and 2017 [5]. The participants ranged in age from 60 to 74 years and were predominantly male (70.5 %). A similar number of patients were classified into intermediate-risk (52.3 %) and high-risk (47.7 %) groups based on their index colonoscopy. By the end of follow-up, 64 544 surveillance episodes were registered. During the surveillance episodes (S1, S2, S3), the yield of advanced adenoma and CRC were analyzed according to assigned risk group. At S1, advanced adenoma and CRC were detected in 10.0 % and 0.5 % respectively, in the entire cohort. When analyzed by subgroup, advanced adenoma yield was higher in the high-risk group (12.2 %) than in the intermediate-risk group (8.0 %), whereas CRC yield was similar in both groups (high risk 0.5 % vs. intermediate risk 0.4 %). As expected, advanced adenoma and CRC yields declined between S1 and S2. The yield at S1 was lowest among patients with only one index adenoma ≥ 10 mm (advanced adenoma 6.1 %; CRC 0.3 %). Finally, the incidence of CRC was lower in the surveillance cohort compared with that in the general population (standard incidence ratio 0.76, 95 %CI 0.66–0.88).

The key findings were that the detection yield of advanced adenoma and CRC at surveillance was reassuringly low. This indicates that a high-quality index colonoscopy together with subsequent surveillance is effective at reducing the risk of missed and metachronous CRC, with the most significant benefit achieved by the initial examination. Furthermore, the authors investigated factors that could potentially alter current surveillance protocols and found that individuals with a single adenoma ≥ 10 mm had a low likelihood of having additional adenomas found on surveillance follow-up (6.1 %). Hence, it is possible that this group could avoid surveillance by colonoscopy, especially as it represents almost one-third of all surveillance cases. Removing this cohort from surveillance programs would result in a substantial reduction in workload and burden of colonoscopy for these patients. In contrast, factors that were identified to increase the likelihood of advanced adenoma at S1 were male sex, current smoker, consuming ≥ 15 units of alcohol per week, and American Society of Anesthesiologists physical status score ≥ 2; despite a modest increment, these factors might potentially inform risk stratification strategies. Curiously, the study did not find any significant association between body mass index and advanced adenoma, which conflicts with previous studies that have shown an increased risk of advanced adenoma in obese individuals [6] [7]; this inconsistency warrants further investigation into the role of body mass index. Importantly, the study did not differentiate between right-sided and left-sided advanced adenoma, which could be important for tailoring surveillance strategies given the differing characteristics and prognoses of these lesions [8]. For CRC, multivariable analysis demonstrated an increased risk with age and for patients with multiple adenomas (≥ 6) at index colonoscopy. Interestingly, factors typically impacting CRC risk in the general population such as male sex, smoking status, and high body mass index, were not associated with surveillance CRC risk in this study.

There are some limitations to the study that should be borne in mind when interpreting the results. The study was conducted within an organized surveillance program with highly experienced endoscopists, and as such, the findings may not be generalizable to other healthcare settings. The statistical power of the study may be limited by the lack of a sample size calculation and the fact that only a small number of CRCs were detected. In addition, recognition of the importance of serrated polyps only started to emerge during the study period and, as a result, serrated lesions were not formally evaluated and conclusions about their impact cannot be drawn. Finally, the authors did not account for multiple testing, so the results should be interpreted accordingly.

Overall, this study carries an important message regarding patients with colorectal adenomas removed by colonoscopy. First, it shows that the general risk of advanced adenoma and CRC during surveillance is low compared with the general population. Second, it identifies particular factors that may influence the risk of subsequent CRC and advanced adenoma, and these might be helpful in informing future surveillance recommendations. Finally, it reveals that a high-quality index colonoscopy, combined with proper identification of the patients at highest risk, might improve the functioning of overburdened CRC screening and surveillance programs.

Publication History

Article published online:
28 June 2023

• References

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