The resect and discard strategy: a new kid on the block?

Approximately 90 % of polyps detected and removed during screening colonoscopy are smaller than 10 mm [1]. The vast majority of these lesions, especially diminutive polyps (1–5 mm), do not contain colorectal cancer (CRC) or advanced histology, such as villous histology or high grade dysplasia. Yet, in most of our practices, all resected polyps, including diminutive lesions, are routinely sent for histological analysis.

The main reason for a formal histological assessment is to determine the appropriate interval to the next surveillance examination. However, histological evaluation of these diminutive lesions is expensive and time-consuming, and with the continued improvement in endoscopy image quality and the development of artificial intelligence (AI)-based detection systems, it is very likely that the prevalence of these lesions will only increase in the coming years.

“The work of Duong et al. is relevant because use of the PBRD strategy significantly reduced the number of pathological examinations required and may help to overcome the perceived barriers associated with adoption of an optical diagnosis-based discard strategy.”

Instead of sending these lesions to a pathologist, a real-time endoscopic diagnosis by the endoscopist could replace formal histopathological analysis, thereby improving the cost-efficacy of colonoscopy. A diagnosis by the endoscopist is called an “optical diagnosis” and contains two strategies. First, all diminutive polys throughout the colon can be removed and discarded without formal histological analyses (resect and discard strategy); the optical diagnosis of the endoscopist is used to assign a surveillance interval. Second, hyperplastic polyps in the rectosigmoid can be left in situ, reducing unnecessary polypectomies (diagnose and leave strategy). Before such strategies can be implemented in daily practice, a high diagnostic accuracy should be achieved by endoscopist performing such optical diagnosis. In 2011, the American Society for Gastrointestinal Endoscopy published a guideline in which such performance thresholds were recommended. This Preservation and Incorporation of Valuable Endoscopic Innovation (PIVI) stated that endoscopist should achieve at least ≥ 90 % agreement between surveillance intervals predicted by optical diagnosis compared with surveillance interval assignments based on histological assessment [2]. A ≥ 90 % negative predictive value should also be achieved in order to leave hyperplastic polyps in situ in the rectosigmoid [2].

In 2019, the European Society of Gastrointestinal Endoscopy (ESGE) stated that virtual chromoendoscopy (e. g. narrow-band imaging) and dye-based chromoendoscopy can be used, under strictly controlled conditions, for real-time optical diagnosis of diminutive polyps performed by experienced endoscopists who are adequately trained [3]. To date, however, despite many studies, efforts, and guideline statements, the optical diagnosis strategy has still not been widely implemented. A recent study revealed that the most important barriers to implementation are fear of making an incorrect diagnosis, assigning incorrect surveillance intervals, and medico-legal consequences [4]. In addition, without a strict and rigorous training program, it appears that achieving and maintaining the PIVI thresholds remains challenging, which is especially true for the 90 % negative predictive value threshold in the rectosigmoid [5].

The study by Duong at al. in this issue of Endoscopy is a retrospective study reporting a simplified polyp-based resect and discard strategy that assigns surveillance intervals based only on size and number of small and diminutive polyps, without the need for pathology or an optical diagnosis [6]. The study included 452 patients and the majority of colonoscopies were performed for surveillance, screening, or symptoms. The primary aim of the study was to test a polyp-based resect and discard (PBRD) strategy that assigns surveillance intervals not based on histology, but on common scenarios based on size and number of small colorectal polyps (< 10 mm). The primary study end point was defined as the surveillance interval agreement of the PBRD strategy compared with pathology-based management according to the 2020 US Multi-Society Task Force on Colorectal Cancer (USMSTF) guidelines [7]. The authors reported an excellent 97.8 % surveillance agreement with pathology-based management when using the PBRD strategy. In addition, the PBRD strategy reduced pathological examinations by almost 60 % while providing almost 88 % of patients with immediate surveillance interval recommendation on the day of the colonoscopy compared with only 47 % when pathology-based management was used.

The work of Duong et al. is relevant because use of the PBRD strategy significantly reduced the number of pathological examinations required and may help to overcome the perceived barriers associated with adoption of an optical diagnosis-based discard strategy. A major advantage of the PBRD approach is that it can be introduced easily because endoscopists do not require prior training. Moreover, as surveillance intervals are based on the size of polyps instead of an optical diagnosis, fear of making an incorrect diagnosis is no longer an issue.

The PBRD strategy also has some limitations however. The diagnose and leave strategy is not incorporated and thus, theoretically, all polyps should be removed, including hyperplastic polyp-appearing lesions in the rectosigmoid. Another issue that deserves attention is the inclusion of small (6–9 mm) polyps in the PBRD scenarios. Although small polyps have a relatively low risk of harboring advanced histology, T1 cancers do occur in polyps 5–9 mm in size and these small lesions are often not recognized as such by the endoscopist [8]. By including polyps of 6–9 mm in size, there is a potential risk that T1 cancers are resected and discarded without histological analysis, and that patients are not staged and monitored according to a T1 CRC guideline. Given the difficulties experienced to date in implementing any strategy, I therefore believe that we should first focus on the introduction of a discard strategy in any form for diminutive (1–5 mm) lesions before we expand our approach to polyps of 6–9 mm.

We stand on the threshold of the introduction of AI detection and computer-aided diagnosis classification systems in routine endoscopy practice. Most likely, a widespread use of these systems will lead to a paradigm shift in how we manage diminutive, small, and perhaps also larger polyps. The future will tell us whether these AI systems live up to our expectations and whether they provide us with greater opportunities to safely discard polyps while reducing costs. Until then, a PBRD-like approach could be an attractive alternative and certainly deserves further investigation in prospective studies.

Publikationsverlauf

Artikel online veröffentlicht:
12. August 2021

• References

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