Background: The impact of not referring sub-centimetre polyps identified at CT colonography upon the efficacy of colorectal cancer screening remains uncertain.
Aim: To determine the distribution of advanced neoplasia according to polyp size in a screening setting.
Methods: Published studies reporting the distribution of advanced adenomas in asymptomatic screening cohorts according to polyp size were identified by MEDLINE and EMBASE searches. Predefined outputs were the screening rates of advanced adenomas represented by diminutive (< or =5 mm), small (6-9 mm), sub-centimetre (<10 mm) and large (> or =10 mm) polyp sizes.
Results: Data from four studies with 20 562 screening subjects met the primary inclusion criteria. Advanced adenomas were detected in 1155 (5.6%) subjects (95% CI = 5.3-5.9), corresponding to diminutive, small and large polyps in 4.6% (95% CI = 3.4-5.8), 7.9% (95% CI = 6.3-9.4) and 87.5% (95% CI = 86-89.4) of cases respectively. The frequency of advanced lesions among patients whose largest polyp was diminutive, small, sub-centimetre and large in size was 0.9%, 4.9%, 1.7% and 73.5% respectively.
Conclusions: Based on this systematic review, a 6-mm polyp size threshold for polypectomy referral would identify over 95% of subjects with advanced adenomas, whereas a 10-mm threshold would identify 88% of cases.