What is the nature of polyps detected by the NHS bowel cancer screening pilots?

Aim The NHS Bowel Cancer Screening Programme is currently being introduced following three rounds of pilot screening. The study outlines the important characteristics of polyps detected by pilot screening and compares the location of polyps with those of symptomatic cancers to challenge the circumstantial evidence for the adenoma carcinoma pathway. Method The first 100 patients with screen-detected polyps from University Hospitals Coventry and Warwickshire (UHCW) were identified from the colorectal cancer screening database. Important characteristics of the polyps were identified from the endoscopy reporting system and entered into a database. Polyp location was compared with the location of symptomatic cancers detected in the UHCW colorectal cancer database. Results One hundred patients were selected for investigation and 202 polyps were detected. The average age of the patients with polyps was 61 years, 35% were under the age of 60. There were 67% male subjects. The average size of the largest polyp in each of the different patients was 13.5 mm. Eighty-five per cent of polyps were excised. Histology was available for 181 polyps of which 40% were tubulovillous, 33% tubular, 14% metaplastic and 1% villous. Eighty-eight per cent showed low-grade dysplasia and 8% high-grade one. The location of screen-detected polyps was significantly different from that of symptomatic cancers in our database, with proportionally more sigmoid and proportionally less rectal and caecal polyps detected. Conclusion The study outlines the important characteristics of screen-detected polyps. The significant difference in location of polyps from that of cancer suggests a variation in the malignancy potential of polyps depending on the location.