Evaluation of the polyp-based resect and discard strategy: a retrospective study

• Abstract
• Introduction
• Methods
• Study population
• The PBRD strategy
• Study outcomes
• Clinical adherence to pathology-based guidelines
• Sample size and statistical analysis
• Results
• Patient and polyp characteristics
• PBRD strategy surveillance interval recommendations
• Clinical adherence to pathology-based surveillance intervals
• Discussion
• References

Abstract

Background Standard colonoscopy practice requires removal and histological characterization of almost all detected small (< 10 mm) and diminutive (≤ 5 mm) colorectal polyps. This study aimed to test a simplified polyp-based resect and discard (PBRD) strategy that assigns surveillance intervals based only on size and number of small/diminutive polyps, without the need for pathology examination.

Methods A post hoc analysis was performed on patients enrolled in a prospective study. The primary outcome was surveillance interval agreement of the PBRD strategy with pathology-based management according to 2020 US Multi-Society Task Force guidelines. Chart analysis also evaluated clinician adherence to pathology-based recommendations. One-sided testing was performed with a null-hypothesis of 90 % agreement with pathology-based surveillance intervals and a two-sided 96.7 % confidence interval (CI) using correction for multiple testing.

Results 452 patients were included in the study. Surveillance intervals assigned using the PBRD strategy were correct in 97.8 % (96.7 %CI 96.3–99.3 %) of patients compared with pathology-based management. The PBRD strategy reduced pathology examinations by 58.7 % while providing 87.8 % of patients with immediate surveillance interval recommendations on the day of colonoscopy, compared with 47.1 % when using pathology-based management. Chart analysis of surveillance interval assignments showed 63.3 % adherence to pathology-based guidelines.

Conclusion The PBRD strategy surpassed the 90 % agreement with the pathology-based standard for determining surveillance interval, reduced the need for pathology examinations, and increased the proportion of patients receiving immediate surveillance interval recommendations. The PBRD strategy does not require expertise in optical diagnosis and may replace histological characterization of small and diminutive colorectal polyps.

Introduction

The current standard of colonoscopy practice is to remove colorectal polyps and to send them for histological characterization [1] [2]. However, the vast majority of polyps found during colonoscopies are small (< 10 mm) and diminutive (≤ 5 mm), and harbor a low potential for advanced pathology or malignancy. Furthermore, histological characterization is costly and delays the time to clinical decision making in terms of timing of a subsequent colonoscopy [3] [4] [5] [6]. Especially in the context of screening and surveillance colonoscopies, the pathology results are needed to determine the next surveillance interval [1]. Foregoing histological characterization of small polyps may thus improve the cost efficiency of routine colonoscopy practice while allowing endoscopists to provide immediate surveillance interval assignment on the day of the colonoscopy.

The approach of replacing pathology examination with other modalities (e. g. image-enhanced optical polyp diagnosis) is not new and is typically referred to as the “resect and discard” strategy [7]. However, the resect and discard strategy has some limitations. It requires the endoscopist to assign a level of confidence to the optical diagnosis, which can be difficult to standardize in a real-life setting [8]. Additionally, polyps diagnosed with low confidence must still undergo resection and histological characterization, which reduces the ability to deliver immediate surveillance interval recommendations. Furthermore, optical polyp diagnosis requires training and, according to a recent survey, 84.2 % of surveyed endoscopists have not adopted a resect and discard strategy and 59.9 % think this approach is not feasible in its current form [9].

The primary aim of this study was to test a simplified polyp-based resect and discard (PBRD) strategy that requires no optical diagnosis or histological characterization, and to compare the concordance of this strategy with pathology-based surveillance interval assignment. The secondary aims of this study were to measure surveillance interval agreement for patients with only diminutive polyps or only small polyps, the percentage of pathology examinations avoided, and the number of surveillance intervals that can be given on the same day as the colonoscopy when using the PBRD strategy.

Methods

Study population

The study was designed as a proof-of-concept post hoc analysis of a patient cohort enrolled into a single-center, prospective, colonoscopy study (institutional review board [IRB] approval number CER 16.367; ClinicalTrials.gov NCT04032912), the aim of which was to evaluate different resect and discard strategies. This study database was chosen because it contained prospectively collected data of relevant information such as cohort demographics, endoscopy and pathological polyp information, personal or family history of colorectal cancer (CRC), as well as data on the colonoscopy procedure (i. e. sedation, bowel preparation quality, withdrawal time). The prospective study included patients in the recommended screening age range (45–80 years), and excluded patients with known or suspected inflammatory bowel disease or familial polyposis syndrome, active colitis at colonoscopy, coagulopathy, poor general health (defined as an American Society of Anesthesiologists class > 3), or patients presenting for emergency colonoscopy. As the present study aimed to evaluate surveillance interval assignment after polypectomy, patients with a personal history of CRC, or patients diagnosed with a CRC or a metastatic cancer during the study colonoscopy were excluded. Furthermore, patients undergoing colonoscopy for an interventional endoscopic procedure such as endoscopic mucosal resection that required more intense procedure-related surveillance intervals were excluded from the analysis. Patients with missing or incomplete polyp pathology results were also excluded from the study. The local IRB approved this post hoc analysis of the prospective study database including an additional complementary chart review (IRB approval number CER 17.242). All colonoscopy procedures were performed as per standard of care using high definition Pentax (Tokyo, Japan) colonoscopes, and all polyps found during the colonoscopies were removed using standard polypectomy techniques and sent for pathology examination according to standard of care and institutional routine practice.

The PBRD strategy

The primary aim of the analysis was to test a simplified PBRD strategy that assigns surveillance intervals for common scenarios based on size and number of small colorectal polyps ( < 10 mm). The PBRD strategy was developed through discussions between four researchers (R.D., D.vR., H.P., A.N.B.). Several clinical scenarios were created based on the most common situations ( [Table 1]).

A benchmark of at least 90 % agreement of surveillance interval with pathology-based recommendations was adopted, as has been recommended by the American Society for Gastrointestinal Endoscopy (ASGE) in order for a resect and discard strategy to be implemented in clinical practice and to replace pathology examinations [10]. Additionally, the European Society of Gastrointestinal Endoscopy has also recently recommended the adoption of a resect and discard strategy instead of pathological diagnosis [11]. The study hypothesis was that the PBRD strategy would achieve the benchmark proposed by the ASGE.

Study outcomes

The primary outcome was the surveillance interval agreement between the PBRD strategy and the pathology-based 2020 US Multi-Society Task Force on Colorectal Cancer (USMSTF) surveillance interval recommendations. Secondary outcomes included: surveillance interval agreement for patients with only diminutive polyps or only small polyps; percentage of pathology examinations avoided; percentage of surveillance intervals that could be given on the same day as the colonoscopy. A trained researcher assigned surveillance intervals for patients by using both the PBRD strategy and the pathology-based reference standard, while a second researcher (A.D.) randomly reviewed surveillance interval assignment for 118 patients (26.1 %) for quality assurance. The current USMSTF guideline recommends 3–5, 5–10, and 7–10-year surveillance intervals for some polyp pathologies. For such cases in the current study, the longest interval was chosen as the reference surveillance interval when comparing both strategies. For calculation of the pathology-based surveillance intervals, first-degree family history of CRC and inadequate bowel preparation were taken into account according to current guideline recommendations [1] [2] [12] [13] [14]. Bowel preparation was considered adequate if the documented total Boston Bowel Preparation Scale score was ≥ 6, with all three colonic segments having an individual score of ≥ 2. Pathology results were used to calculate overall polyp detection and adenoma detection rates.

Clinical adherence to pathology-based guidelines

An additional analysis included a retrospective clinical chart review of the study cohort to evaluate clinical adherence to pathology-based surveillance interval guidelines as per written recommendations in the charts of included patients. Surveillance interval assignments from physicians were collected from the medical files (endoscopy reports, clinical notes, and/or letters to the referring physician), and were compared with surveillance intervals calculated based on pathology results and contemporaneous USMSTF recommendations [1]. Patients were excluded from this analysis if their medical records did not include a written numerical surveillance interval recommendation from their treating physician or if the treating physician recommended discontinuation of colonoscopy surveillance. Any surveillance interval recommendation made by the physician that was within a range of ±6 months of the USMSTF recommendation was deemed a correct surveillance interval assignment. In situations where the physician recommended a range of intervals, the suggested range of intervals was deemed correct if all of the values within that range matched the pathology-based reference standard surveillance interval suggestion. For instance, if a physician recommended a 5–7-year follow-up and the reference standard suggested a 5–10-year follow-up, the physician’s recommendation was deemed correct. However, if the physician recommended a 5–7-year follow-up but the reference standard recommended only a 5-year follow-up, the clinical recommendation was deemed incorrect.

Sample size and statistical analysis

The adopted sample size was based on an assumption that the PBRD strategy would reach a 92 % agreement with the pathology-based reference standard. Assuming a 92 % surveillance interval agreement (power 0.8, alpha 0.05, precision 0.025), at least 452 patients needed to be enrolled into the study. To compensate for a potential 15 % exclusion rate from the used database (i. e. missing pathology results, history of CRC or diagnosis of CRC, interventional endoscopy-related procedures), 544 consecutive patients were screened for study inclusion.

The study was considered exploratory in nature due to the number of analyses to be performed. For the statistical analysis, normally distributed variables describing baseline characteristics are presented as means with standard deviations (SDs). Descriptive analysis in presentation of crude numbers and proportions was used to present patient, procedure, and polyp outcomes.

A one-sided Z test was performed with a null-hypothesis of 90 % agreement with pathology-based surveillance intervals. As the main outcome was retested for only small polyps and only diminutive polyps, a two-sided 96.7 % confidence interval (CI) was calculated for those outcomes using the Bonferroni correction (α/3) with α = 0.05. Stata version 16 (StataCorp, College Station, Texas, USA) was used for all statistical analyses.

Results

Patient and polyp characteristics

From the study database, 544 consecutive patients were screened for inclusion. Seven patients were excluded from this study because a CRC was found at colonoscopy/pathology (see Table 1 s in the online-only Supplementary material). After applying the exclusion criteria, 452 patients were included in the final analysis ([Fig. 1]). The mean age of the study population was 62 years (SD 8.7), 49.6 % were female, and the mean body mass index was 27.4 kg/m². Bowel preparation was adequate in 86.5 % of patients. The majority of colonoscopies were performed for screening (35.8 %) and surveillance (23.2 %) indications ([Table 2]). The polyp detection rate was 61.1 % and the adenoma detection rate was 40.7 %.

Of the 566 polyps detected in this study, 316 (55.8 %) were neoplastic, of which 275 (48.6 % of the overall findings) were tubular adenomas ([Table 3]). The mean size of polyps was 4.6 mm (SD 3.9). Overall, 439 diminutive polyps (77.6 %) and 523 small polyps (92.4 %) were found in the study cohort. A total of 27 polyps (4.8 %) were classified as sessile/serrated adenomas/polyps (SSA/Ps), and 2 polyps (0.4 %) contained high grade dysplasia.

PBRD strategy surveillance interval recommendations

When using the PBRD strategy, the assigned surveillance intervals were correct in 97.8 % (96.7 %CI 96.3 %–99.3 %) of patients based on the 2020 USMSTF guideline. The PBRD strategy suggested a shorter surveillance interval for 0 patients and a longer surveillance interval for 10 patients (2.2 %) compared with pathology-based surveillance intervals. An additional analysis was performed for patients with only diminutive polyps (any patient without a polyp or with at least one polyp that was ≥ 6 mm was excluded). For these patients (n = 193), the PBRD strategy assigned correct surveillance intervals for 95.9 % (n = 185; 96.7 %CI 92.8 %–98.9 %) and incorrect intervals for 8 (0 were shorter intervals and 8 [4.1 %] were longer). Another analysis was performed for patients with only small polyps (any patient without a polyp or with at least one polyp that was ≥ 10 mm was excluded). For these patients (n = 244), the PBRD strategy assigned correct surveillance intervals for 95.9 % (n = 234; 96.7 %CI 93.2 %–98.6 %) and incorrect intervals for 10 (0 were shorter intervals and 10 [4.1 %] were longer).

[Table 4] shows the concordance between the PBRD strategy and the pathology-based reference standard. Six patients (1.3 %) received a 10-year surveillance interval recommendation when using the PBRD strategy while receiving a 3-year surveillance interval when using the pathology-based reference standard. All patients had a diminutive polyp with either a traditional serrated adenoma or an adenoma with villous histology. Four patients (0.9 %) received a 10-year surveillance interval recommendation when using the PBRD strategy while receiving a 5-year surveillance interval when using the pathology-based reference standard.

When using the PBRD strategy, 234 polyps (41.3 %) would need to be sent for pathology examination compared with 566 polyps when using the pathology-based reference standard, thus removing 58.7 % of pathology examinations. In addition, when using the PBRD strategy, 397 patients (87.8 %) could receive an immediate surveillance interval recommendation compared with 213 (47.1 %) when using the pathology-based reference standard.

Clinical adherence to pathology-based surveillance intervals

Among the 452 patients included in the analysis, 294 (65.0 %) had written numerical documentation of the next surveillance interval in their clinical charts ([Fig. 1]), of whom 186 (63.3 %) had physician-recommended surveillance intervals that were in agreement with a post hoc calculation based on pathology results and the contemporaneous USMSTF guideline as the reference standard.

Discussion

This study compared a novel PBRD strategy for colonoscopy surveillance interval assignment of small colorectal polyps with the surveillance intervals determined based on pathology results when using the 2020 USMSTF recommendation. We found a 97.8 % agreement rate, which surpassed the proposed 90 % ASGE benchmark [10]. We found that when using the PBRD strategy, about 60 % of pathology examinations could be avoided, and nearly 90 % of patients could be provided with an immediate post-colonoscopy surveillance interval recommendation compared with only 47.1 % of patients when using pathology for all polyps. Furthermore, low clinical adherence (63.3 %) to contemporaneous guideline recommendations was observed from a clinical chart review at our institution. Therefore, implementation of the PBRD strategy has the potential to improve the cost efficiency of colonoscopy practice as well as making communication of subsequent surveillance intervals easier and less prone to error.

The PBRD strategy reached a high agreement rate with pathology-based recommendations because almost all small and diminutive colorectal polyps are either benign or low risk adenomas [4] [5]. In the most recent 2020 USMSTF guideline, a 10-year surveillance interval recommendation will have a high likelihood of being correct, even without knowing the exact pathology result, as most small or diminutive polyps are either hyperplastic or low risk adenomas. Our results show that knowing the size and number of polyps found during colonoscopy can be sufficient to accurately predict the next surveillance interval. This approach is likely to be safe, as a recent prospective study including 36 107 polyps measuring ≤ 5 mm and 6523 polyps measuring 6–9 mm did not find any cancers among small polyps [15]. Other studies have confirmed the low risk of finding CRC and advanced histology among polyps measuring 1–9 mm [16] [17] [18] [19] [20] [21].

This is the first study to compare a resect and discard strategy that does not require optical diagnosis with pathology-based results and to include the adherence of physicians’ surveillance intervals to guideline recommendations in clinical practice. The PBRD strategy outperformed the adherence to recommended surveillance intervals at our institution. This phenomenon is not limited to our institution; a recent systematic review showed that adherence to guideline surveillance intervals in clinical practice is low [22]. Therefore, the PBRD strategy, if implemented in clinical practice, could theoretically improve clinical adherence to guidelines. However, this will need to be tested in future studies.

When using the PBRD strategy, only 10 patients (2.2 %) received a longer interval recommendation compared with the surveillance interval proposed by the pathology-based reference standard. Notably, 6 patients (1.3 %) with high risk polyps received a 10-year recommendation as opposed to a 3-year surveillance interval. This is lower than the 15 % (95 % CI 6.4 %–26 %) of patients in high risk groups who receive a longer surveillance interval assignment than recommended in clinical practice as described in the literature [17]. However, this could create a barrier for the uptake of the PBRD strategy, as assigning longer surveillance intervals to some high risk lesions might be inherent to the strategy. This unavoidable risk by design can also be found in pathology-based surveillance intervals in situations such as unretrieved polyps, polyps crushed with forceps which are then impossible to diagnose, and interobserver disagreement between pathologists for diagnosing SSAs and advanced histology [23] [24] [25]. However, this problem is common for all optical diagnosis-based resect and discard strategies, as most optical diagnosis classifications such as SIMPLE, WASP, and NICE do not present criteria to distinguish between traditional serrated adenomas and SSA/Ps or between low and high grade dysplasia [26] [27] [28]. The inclusion of atypical morphology criteria such as those in the Paris classification could provide a solution to this problem. Furthermore, revised models limiting the PBRD strategy to diminutive polyps only should be studied. However, there is also recent evidence that advanced histologic features in diminutive polyps do not contribute to metachronous CRC [29].

Implementing a PBRD strategy could improve post-colonoscopy management of patients. A considerable number of patients could receive an immediate surveillance interval after their colonoscopy if the PBRD strategy was used. Using the PBRD strategy could allow endoscopists and patients to forgo pathology follow-ups, which would save time and simplify clinical practice [30]. Additionally, although a cost-saving analysis was beyond the scope of this study, the PBRD strategy will likely reduce colonoscopy-associated costs by reducing the number of pathology examinations [6] [7] [31] [32]. Going forward, the inclusion of cost-effectiveness analyses in subsequent studies on the subject may be advantageous to further assess the benefits of the proposed strategy. The colonoscopy quality metrics in the evaluated cohort were good, with a polyp detection rate of 61.1 % and adenoma detection rate of 40.7 %. However, post-colonoscopy quality metrics were poor, with 148 patients (33.7 %) having no written surveillance interval recommendation in their charts. Implementing a PBRD strategy could improve the number of patients with a written surveillance interval recommendation directly after their colonoscopy. Furthermore, the PBRD strategy does not require optical diagnostic skills, which is relevant as most endoscopists cite concern about making an incorrect optical diagnosis as the main barrier to implementation of the resect and discard strategy [9]. The PBRD strategy also does not require any auditing or photo-documentation, as recommended by the ASGE for implementing resect and discard strategies [10], with its attendant costs.

With the development of artificial intelligence (AI)-based optical diagnosis, the current trend is toward assisting endoscopists with technology for optical diagnosis [33]. Studies that have looked at the use of AI to assist in the real-time diagnosis of polyps have shown promise, with a recent meta-analysis indicating high accuracy, although included study designs were highly variable and no study using AI in community-based practice is available yet [34]. There also might be issues with the ability of different endoscopists to adequately present a polyp for AI analysis, which will need to be explored. Furthermore, current AI technology does not make the distinction between low and high grade dysplasia, and faces the same problem of potentially removing a cancer or high grade dysplastic lesion without appropriate follow-up [9]. Additionally, AI sometimes provides low confidence diagnoses. In such cases, supplementary strategies such as the PBRD strategy or a location-based resect and discard strategy can be used to help the AI-based decision [35]. However, with different strategies emerging, we can be confident that the resect and discard strategy will become reality in the foreseeable future, either through advanced technology or through models such as the PBRD strategy for endoscopists who do not have access to the latest technology.

Several study limitations need to be mentioned. First, this was a post hoc analysis of a dataset obtained from a prospective colonoscopy study. Therefore, the PBRD strategy should be confirmed using a larger patient sample in a prospective clinical study. Second, the PBRD strategy does not have a clinical scenario that proposes a 3-year surveillance interval recommendation, unlike the 2020 USMSTF guideline, which recommends a 3-year follow-up for most high risk scenarios [14]. A small percentage of patients therefore receive delayed surveillance intervals. Some adjustments to the PBRD strategy are therefore likely to be required when planning subsequent studies on assessment of the strategy, such as the inclusion of polyp morphology criteria (Paris classification). Forgoing optical diagnosis in favor of polyp size could make endoscopists complacent about thoroughly evaluating polyp appearance, leading to high risk lesions being missed. However, we recommend that every polyp should be closely examined for high risk lesions in our PBRD strategy, and Paris IIc or III morphology should be sent for pathology examination. The necessity of storing the first three polyps in a pathology jar during endoscopy in case > 3 polyps are detected might marginally decrease the cost savings. However, the price of the specimen pots is likely negligible compared with savings in pathologist time and cost when using the PBRD strategy. The study excluded patients who had missing or incomplete pathology results, which could have led to some selection bias. The PBRD strategy also depends on subjective polyp size characterization to recommend a surveillance interval; however, most resect and discard research uses similar methods for assessing polyp size.

In summary, the PBRD strategy surpassed the 90 % concordance with the pathology-based reference standard for post-colonoscopy surveillance interval assignment. The proposed strategy may simplify colonoscopy practice by decreasing the number of pathology examinations and increasing the number of patients who can receive immediate surveillance interval recommendations after their colonoscopies, while also reducing the need for follow-up appointments and simplifying communication to referring physicians about pertinent pathology results.

Competing interests

Daniel von Renteln is supported by a “Fonds de Recherche du Québec Santé” career development award. He has also received research funding from ERBE, Ventage, Pendopharm, and Pentax, and is a consultant for Boston Scientific and Pendopharm. All other authors declare that they have no conflicts of interest.

Acknowledgments

The findings, statements, and views expressed are those of the authors and do not represent the views of the Department of Veterans Affairs or the United States Government. The outcomes and analysis of this project have been presented at the Canadian Digestive Diseases Week 2019, ESGE Days 2019 and Digestive Disease Week 2019.

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Corresponding author

Publication History

Received: 15 February 2020

Accepted: 09 February 2021

Accepted Manuscript online:
09 February 2021

Article published online:
15 April 2021

© 2021. Thieme. All rights reserved.

Georg Thieme Verlag KG
Rüdigerstraße 14, 70469 Stuttgart, Germany

• References

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  Search in Google Scholar
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  Search in Google Scholar
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