WHO eliminates one of three diagnostic criteria for serrated-polyposis syndrome

Last Updated: 2020-02-04

By Will Boggs MD

NEW YORK (Reuters Health) - In its update of criteria for diagnosing serrated-polyposis syndrome (SPS), the World Health Organization (WHO) has slightly altered two criteria and eliminated another altogether.

"The most controversial aspect of SPS diagnosis is the fact that diagnosis is based on arbitrary clinical criteria," said Dr. Arne G. C. Bleijenberg of Amsterdam UMC.

"It has been well established that these criteria indeed identify individuals with an increased risk of colorectal cancer (CRC) that need stringent endoscopic surveillance," he told Reuters Health by email. "However, the criteria are still arbitrary and imply that there is a black-and-white difference between individuals that fulfill the criteria and those that do not fulfill the criteria."

Dr. Bleijenberg and colleagues review the differences between WHO's 2010 criteria and the updated 2019 criteria in their report in Gastroenterology.

The 2010 version included three diagnostic criteria: I) at least 5 serrated polyps proximal to the sigmoid colon with two or more of these being >10 mm; II) any number of serrated polyps proximal to the sigmoid colon in an individual who has a first-degree relative with SPS; III) >20 serrated polyps of any size, but distributed throughout the colon.

The 2019 version eliminated criterion II, because these patients were considered to have a lower CRC risk than those who fulfilled criteria I and/or III. Although this represents a diagnostic change, it does not eliminate the need for regular endoscopic surveillance, because these patients remain first-degree relatives of SPS patients.

"The omission of the 'old' criterion II represents the most important change compared to the previous diagnostic criteria," Dr. Bleijenberg said. "Abandonment of this criterion follows an ongoing debate about its relevance."

The old criterion I only included polyps proximal to the sigmoid colon, whereas the new criterion now includes serrated polyps in the sigmoid colon. And all serrated polyps now only have to be at least 5 mm, rather more than 10 mm.

The old criterion III became the new criterion II with few changes. Among the >20 serrated polyps distributed throughout the colon, at least five must now be proximal to the rectum to make the diagnosis.

For patients previously diagnosed with SPS by the old criterion II, the authors recommend not to withdraw that diagnosis but to study the CRC risk of such individuals that now fall just short of an SPS diagnosis.

Although international guidelines recommend stringent endoscopic surveillance regimens after initial polyp clearance, the CRC risk varies among SPS patients, and the authors of this report advocate further studies aimed at improving personalized treatment protocols.

Specifically, they suggest that surveillance intervals might be extended beyond two years for patients fulfilling only the new criterion II, but this should be carried out with caution and as part of prospective studies.

"Unfortunately, at this moment it does not seem plausible that a single objective test, such as a genetic test, will be able to differentiate between patients with vs. without SPS," Dr. Bleijenberg said. "After all, the phenotypic diversity among SPS patients suggests that multiple pathophysiologic substrates might result in a SPS phenotype, and therefore a single test might be insufficient to identify these different substrates."

"Regardless, however, it has been shown over recent years that application of the WHO clinical criteria very effectively identifies a group of individuals with an increased risk of CRC," he said. "In this light, arbitrary as they may be, the updated diagnostic criteria are of high clinical relevance and should be carefully applied by physicians."

"Serrated-polyposis syndrome is, unlike many physicians assume, not a rare disease: up to 1:111 individuals in fecal immunochemical test (FIT)-based screening programs might fulfill the diagnostic criteria," Dr. Bleijenberg said. "Diagnosis is frequently missed because of failure to apply the criteria, according to some studies. Failure to apply the criteria leaves a group of high risk individuals without proper treatment and subsequent endoscopic surveillance."

Dr. James Church of Cleveland Clinic, in Ohio, who has studied serrated polyps, told Reuters Health by email, "SPS is not really a syndrome (there are no extracolonic features to aid in defining phenotype). There is no unifying heritable genetic cause. The criteria are not based on any data. The original criteria were informally invented by two people having coffee, and yet they have driven practice as if they were the gospel truth."

"Patients with multiple hyperplastic or sessile serrated polyps in their colon are at increased risk of colon cancer due to the underlying biological changes in the colorectal mucosa that gave rise to the serrated polyps," he said. "The more serrated polyps there are and the bigger they are, the greater the degree of mucosal instability and the higher the risk. Sessile serrated polyps confer the highest risk and represent the biggest challenge. They deserve the closest surveillance."

"In the absence of a unifying genetic mutation, the risk to family members is based on environmental factors, largely smoking," Dr. Church explained. "The more unstable the patient's colon (as defined by the number, size, and histology of the polyps), the more important it is to scope the first-degree relatives."

"The 'criteria' are not really needed if you understand the biology," he said.

SOURCE: https://bit.ly/2UogcPq Gastroenterology, online January 23, 2020.