• Colorectal Neoplasia
• Gastrointestinal Neoplasia
• Genetics

Serrated polyposis syndrome (SPS) is a recently recognised high risk condition for colorectal cancer (CRC) characterised by the presence of large and/or multiple serrated polyps in the colon.1 ,2 The prevalence of SPS has been previously estimated out of CRC endoscopy-based screening programmes on average risk individuals; in this setting, the prevalence ranged from 0.033% (1/3000 sigmoidoscopies)3 to 0.055% (1/1818 colonoscopies).4 However, Biswas et al 5 recently published a higher prevalence based on a guaiac faecal  occult blood testing (gFOBT) CRC screening programme in the UK (NHS Bowel Cancer Screening Programme). In this programme, between April 2010 and January 2012, 5/755 (0.66%) patients attended for index screening colonoscopy after a positive gFOBT met the WHO criteria for SPS, which represented a 20-fold increase compared with previous estimates.

In agreement with Biswas’ observation, we have noticed a higher than expected number of SPS patients in the institutional CRC screening programme of Barcelona. This programme, based on faecal immunochemical testing (FIT), is performed biannually in individuals between 50–69-years-old (target population: 203 139). Thus, we aimed at assessing the prevalence of SPS in our setting. Between December 2009 and October 2011, we reviewed the endoscopic and pathology records of all patients undergoing screening colonoscopy after a positive FIT in the first round of our CRC screening programme (n=2355). Colonoscopy was performed at two tertiary centres (Hospital Clinic and Hospital del Mar of Barcelona) by experienced endoscopists. SPS was defined according to the WHO criteria: ≥20 serrated polyps throughout the colon or at least five proximal serrated polyps with two ≥10 mm in size. Patients diagnosed with SPS were derived to the High Risk CRC Clinic associated with the programme for further assessment. In total, eight patients were diagnosed with SPS (8/2355, 0.34%). The mean age was 54.8-years-old (±4.3 SD) and 3 (37.5%) were men. The mean number of serrated polyps and adenomas was 25.8 (±12.9 SD) and 4.3 (±4.9 SD), respectively. Clinicopathological features are specified in table 1.

Our results, along with those reported by the NHS Bowel Cancer Screening Programme, highlight that SPS is relatively common in population-based CRC screening programmes based on FOBT. Indeed, between 1/151 and 1/294 patients undergoing colonoscopy after a positive faecal test, are diagnosed with SPS. Stool tests primarily detect cancer over preneoplastic lesions (especially gFOBT compared with FIT); nevertheless, it seems that faecal occult blood tests would also detect SPS. This fact may be due to the frequent association of SPS with synchronous adenomas (up to 25% of our patients had an advanced adenoma), or that multiple serrated lesions in the colon may result in a positive faecal test. Furthermore, the diagnostic yield of serrated polyps in institutional screening programmes is probably increased due to experienced endoscopists, high awareness of serrated polyps, optimal bowel preparation and improved optics (although high-definition endoscopy is not routinely available in our units). Either way, our results and those from Biswas stress the fact that population-based screening programmes based on faecal occult blood detection identify a significant number of SPS patients with a diagnostic yield at least 10-fold greater than sigmoidoscopy-based or colonoscopy-based screening programmes (0.3–0.7% vs 0.03–0.05%). In conclusion, fostering awareness of serrated polyps and polyposis is mandatory in CRC screening programmes. Since these patients and their relatives require specific assessment, experienced high risk CRC units linked to institutional programmes are needed in the decision-making protocols.