Serrated polyposis: prospective study of first-degree relatives.

Introduction: Serrated polyposis (SP) is an infrequent colorectal cancer (CRC) predisposition syndrome. An unidentified genetic defect is believed to play a role in this condition. The risk of SP and/or CRC for first-degree relatives (FDRs) is not yet well known. The aim of our study was to determine the incidence of both SP and/or CRC by studying the FDRs of our index SP cases and to propose an appropriate interval for colonoscopy surveillance in this group.

Methods: From 2005 to December 2011, we prospectively included all patients from our hospital who fulfilled the SP diagnostic criteria. We interviewed FDRs face to face and offered a colonoscopy to those who were 35 years old or older. The study was carried out with conventional and high-definition colonoscopes and chromoendoscopy with indigo carmine at the discretion of a single endoscopist. The samples were assessed by two pathologists. We reviewed the clinical data for CRC diagnosed previously in FDRs.

Results: From 2005, we collected all the new cases of SP and offered a colonoscopy to 95 FDRs of 34 pedigrees. We performed colonoscopies on 78 FDRs (82.1%). The incidence of SP in the FDRs was 32% (25 patients). Seventy-six percent of patients were diagnosed with SP as they had any number of serrated polyps proximal to the sigmoid colon. Only one patient was diagnosed with CRC as a result of the screening colonoscopy. 44.1% of our index cases had an FDR with a diagnosis of CRC.

Conclusion: Our series, which is the largest prospective cohort of FDRs published, reports an elevated incidence of SP in FDRs, thus supporting the need for screening colonoscopy in FDR and its inclusion in the guidelines.