Reply to Castells et al.

The letter by Castells et al. appropriately focuses on the integration between adenomatous and serrated lesions when scheduling postpolypectomy surveillance. In theory, there are at least two possibilities when dealing with patients with two different types of lesions. The first is to generate an evidence-based ranking among the different histological types, in order to classify the patient according to the highest-ranking lesion. For instance, it could be proposed that patients with coexisting adenomatous and serrated lesions should always be classified according to the adenomatous component, down-grading the serrated component. Indeed, the relationship between the features of the adenoma (size, villous component, grade of dysplasia) and the risk of metachronous advanced neoplasia has been well validated, irrespective of the additional presence of serrated polyps. As the Authors admit, there is scarce literature, if any, supporting a higher risk of metachronous advanced neoplasia in those with coexisting lesions compared with those with only adenomas. Thus, by adding a re-stratification of the adenomatous component based on the coexisting serrated component would only dilute the moderate degree of certainty related to the adenomatous component in the first place.

However, to adopt a pure “ranking strategy” would result in the paradox that a patient with low-risk adenoma and high-risk serrated lesion would be classified in the low-risk category compared with a patient with only a high-risk serrated lesion who would be correctly classified in the intermediate- or high-risk category. Thus, the Authors are proposing a second possibility, which is to sum up the two different components in a multi-dimensional risk stratification, with limited consideration of any ranking between the adenomatous and serrated lesions. Despite the lack of supporting evidence, this expert-derived strategy is appealing. First, it prevents the paradox of the “ranking strategy” by always classifying the patient by the most severe lesion. Second, it is extremely cautious, up-grading the perception of risk in several cases that have not yet been explored in the gastrointestinal literature. Third, it is extremely user friendly, and it may be used easily not only by physicians, but by all of the health team involved in running an organized colorectal cancer (CRC) screening program. However, it also contains some drawbacks. Due to technological improvement and higher endoscopist awareness, the detection rate for serrated lesions may be expected to increase rapidly. Thus, a substantial proportion of the patients with low-risk lesions may be reclassified as intermediate because of one additional subcentimetric serrated polyp. The same may easily occur between the intermediate- and the high-risk category. Although the clinical benefit, if any, of this up-shifting of the surveillance population is largely uncertain, the impact on the demand for endoscopy is clear and is sure to be substantial. When considering the limited capacity in endoscopy services, this excess of surveillance may be expected to displace patients from the much more effective CRC screening programs (which will eventually deteriorate), with no improvement in incidence and mortality rates. For these reasons, a possible compromise between the two options could be to systematically classify the patient with coexisting lesions according to the most severe lesion, without permitting the summing up of different histological types.