Patients with more than 10 colonic polyps, of which at least half were serrated, and their first-degree relatives had a risk of colorectal cancer similar to that of patients who met formal diagnostic criteria for serrated polyposis syndrome (SPS), according to a retrospective multicenter study published in the July issue of Gastroenterology (doi: 10.1053/j.gastro.2017.04.003).

Such patients “should be treated with the same follow-up procedures as those proposed for patients with SPS, and possibly the definition of SPS should be broadened to include this phenotype,” wrote Cecilia M. Egoavil, MD, Miriam Juárez, and their associates.

SPS increases the risk of colorectal cancer (CRC) and is considered a heritable disease, which mandates “strict surveillance” of first-degree relatives, the researchers noted. The World Health Organization defines SPS as having at least five histologically diagnosed serrated lesions proximal to the sigmoid colon, of which two are at least 10 mm in diameter, or serrated polyps proximal to the sigmoid colon and a first-degree relative with SPS, or more than 20 serrated polyps throughout the colon. This “arbitrary” definition is “somewhat restrictive, and possibly leads to underdiagnosis of this disease,” the researchers wrote. Patients with multiple serrated polyps who do not meet WHO SPS criteria might have a “phenotypically attenuated form of serrated polyposis.”

For the study, the researchers compared 53 patients meeting WHO SPS criteria with 145 patients who did not meet these criteria but had more than 10 polyps throughout the colon, of which at least 50% were serrated. For both groups, number of polyps was obtained by adding polyp counts from subsequent colonoscopies. The data source was EPIPOLIP, a multicenter study of patients recruited from 24 hospitals in Spain in 2008 and 2009. At baseline, all patients had more than 10 adenomatous or serrated colonic polyps but did not have familial adenomatous polyposis, Lynch syndrome, hamartomatous polyposis, inflammatory bowel disease, or only hyperplastic rectosigmoid polyps.

The prevalence of CRC was statistically similar between groups (P = .4). There were 12 (22.6%) cases among SPS patients (mean age at diagnosis, 50 years), and 41 (28.3%) cases (mean age, 59 years) among patients with multiple serrated polyps who did not meet SPS criteria. During a mean follow-up of 4.2 years, one (1.9%) SPS patient developed incident CRC, as did four (2.8%) patients with multiple serrated polyps without SPS. Thus, standardized incidence ratios were 0.51 (95% confidence interval, 0.01-2.82) and 0.74 (95% CI, 0.20-1.90), respectively (P = .7). Standardized incidence ratios for CRC also did not significantly differ between first-degree relatives of patients with SPS (3.28, 95% CI, 2.16-4.77) and those with multiple serrated polyps (2.79, 95% CI, 2.10-3.63; P = .5).

A Kaplan-Meier analysis confirmed that there were no differences in the incidence of CRC between groups during follow-up. The findings “confirm that a special surveillance strategy is needed for patients with multiple serrated polyps and their relatives, probably similar to the strategy currently recommended for SPS patients,” the researchers concluded. They arbitrarily defined the group with multiple serrated polyps, so they were not able to link CRC to a cutoff number or percentage of serrated polyps, they noted.

Funders included Instituto de Salud Carlos III, Fundación de Investigación Biomédica de la Comunidad Valenciana-Instituto de Investigación Sanitaria y Biomédica de Alicante, Asociación Española Contra el Cáncer, and Conselleria d’Educació de la Generalitat Valenciana. The investigators had no conflicts of interest.