title: Interval cancers in a guaiac-based colorectal cancer screening programme: Consequences on sensitivity.
abstract: Objective To evaluate interval cancers in the population-based colorectal cancer screening programme of Stockholm/Gotland, Sweden. Methods From 2008, individuals aged 60-69 were invited to colorectal cancer screening using biennial guaiac-based faecal occult blood test (Hemoccult®). Interval cancers, defined as colorectal cancer among participants not diagnosed by the screening programme but registered in the Swedish cancer register, were evaluated by cross-checking the screening histories for all cancers in the region 2008-2012. Results Of 203,848 individuals from nine different birth cohorts who participated (∼60%), 4530 (2.2%) tested positive. All invited individuals were followed up for 24 months after invitation. The cancer register reported 557 colorectal cancer, 219 (39.3%) screen-detected cancers and 338 (60.7%) interval cancers, generating both test- and episode sensitivities of approximately 40% and an interval cancer-rate of 17.1/10,000 tests. Among individuals with positive tests without colorectal cancer diagnosed at work-up colonoscopy, 37 interval cancers (10.9%) occurred. There was statistically significant lower sensitivity in women, ranging 22.4-32.2%, compared with 43.2-52.0% in men. Age-group and tumour location were not strongly correlated to screen-detected cancer rates. The programme sensitivity increased by year (20.3-25.0%), with successively more colorectal cancers diagnosed within the expanding programme (11.6-16.2%). Conclusion Interval cancer is a quality indicator of a screening programme. As the interval cancer-rate determined in a well-organized population-based screening programme was actually higher than the screen-detected cancer rate, a change to a more sensitive screening test is indicated. The lower screen-detected cancers among women, and compliance and quality of work-up colonoscopies also need attention.
authors.affiliation: 1 Department of Molecular Medicine and Surgery, Karolinska Institutet, Karolinska University Hospital, Stockholm, Sweden.
authors.forename: Johannes
authors.initials: J
authors.lastname: Blom
authors.affiliation: 2 Department of Oncology-Pathology, Karolinska Institutet and Regional Cancer Centre Stockholm Gotland, Stockholm, Sweden.
authors.forename: Sven
authors.initials: S
authors.lastname: Törnberg
mesh_terms: D000368:Aged; D015179:Colorectal Neoplasms / Q000175:diagnosis / Q000453:epidemiology*; D055088:Early Detection of Cancer; D005260:Female; D006138:Guaiac; D006801:Humans; D008297:Male; D008403:Mass Screening / Q000379:methods / Q000592:standards*; D008875:Middle Aged; D009780:Occult Blood; D011446:Prospective Studies; D012042:Registries; D012680:Sensitivity and Specificity; D013548:Sweden / Q000453:epidemiology
chemical_list: D006138:Guaiac
keywords: Colorectal; faecal occult blood test; interval cancer; population; screening; sensitivity