Simulated performance of flexible sigmoidoscopy-based screening for advanced neoplasia detection in a Greek population

Flexible sigmoidoscopy (FS) is resource-conserving and may increase adherence to colorectal cancer (CRC) screening compared to total colonoscopy. We investigated the diagnostic performance of FS-based screening for advanced colorectal neoplasia (ACN), including advanced adenomatous neoplasms (AANs), advanced serrated lesions (ASLs) and CRCs. Data from 2005 subjects undergoing average-risk screening colonoscopy in a single center in Greece were retrospectively reviewed. Sensitivities of FS-based screening for detecting AANs, ASLs, CRCs or any ACN were simulated on a per-lesion basis, assuming: 1) FS up to the sigmoid-descending junction (FS-1) or splenic flexure (FS-2); 2) colonoscopy referral criteria according to the 4 screening FS trials conducted in UK, Italy, Norway, and USA. Overall, 114 ACNs (93 AANs, 17 ASLs, 4 CRCs) were detected in 102 (5.1%) subjects. The overall sensitivities of FS-1 and FS-2 alone for the detection of any ACN were 41.2% and 54.4%, respectively. Assuming different colonoscopy referral criteria, the estimated sensitivities for any ACN ranged from 48.2-50.9% for FS-1 and 60.5-64% for FS-2. The overall sensitivities were lower for ASLs (FS-1: 35.3-41.2%, FS-2: 41.2-52.9%) compared to those observed for AANs (FS-1: 48.4-51.6%, FS-2: 62.4-66.7%). The difference was particularly pronounced in women, in whom all 4 criteria led equally to a very low sensitivity for ASLs (30%). Implementation of FS-based screening in Greek subjects would have led to the detection of 48-64% of all ACNs. An alarmingly low detection of ASLs among women may call for gender-specific colonoscopy referral strategies.