Background: Flexible sigmoidoscopy (FS) has a higher degree of sensitivity for detecting colorectal neoplasia in the left side of the colon than Hemoccult (H-II). However, no randomized controlled trial has compared a single FS screening with a H-II screening program (annual or biennial) despite the well-documented mortality reduction from colorectal cancer (CRC) in the latter. The aim was to compare the diagnostic yield of colorectal neoplasia in two aged-matched groups from two different randomized screening trials; one group screened by a single FS+H-II, the other with biennial H-II over the course of 16 years.
Methods: 24,465 persons invited to participate in the Funen biennial H-II screening program were compared with 4,460 similar persons invited to another Funen trial using a single FS+H-II.
Results: Compliance in the biennial H-II program was 65.5% during the first screening round compared to 39.8% for FS+H-II. The cumulative number of persons with positive tests was 8.2% (positive H-II) in the biennial H-II program during 16 years and 20.3% (polyps > 3 mm in diameter seen at FS or positive H-II) for once-only FS+H-II. The diagnostic yield of CRC per 1,000 screened was 9.9 in the biennial H-II program and 6.6 after FS+H-II (6.5 and 2.7 per 1,000 invited). The yield of advanced adenomas (> or = 10 mm and/or villous structure and/or severe dysplasia) was 2.3% in the H-II program and 3.3% after FS+H-II among the screened persons, but this difference disappeared when persons invited, but not necessarily screened, were compared (1.5% versus 1.3%).
Conclusion: Screening with H-II in a biennial screening program during 16 years detected more CRCs than a single screening with FS+H-II and a similar number of advanced adenomas.