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BACKGROUND:Colorectal cancer is a leading cause of morbidity and mortality, especially inthe Western world. The human and financial costs of this disease have promptedconsiderable research efforts to evaluate the ability of screening tests todetect the cancer at an early curable stage. Tests that have been considered forpopulation screening include variants of the faecal occult blood test, flexiblesigmoidoscopy and colonoscopy. Reducing mortality from colorectal cancer (CRC)may be achieved by the introduction of population-based screening programmes.OBJECTIVES: To determine whether screening for colorectal cancer using thefaecal occult blood test (guaiac or immunochemical) reduces colorectal cancermortality and to consider the benefits, harms and potential consequences ofscreening. SEARCH STRATEGY: Published and unpublished data for this review wereidentified by: Reviewing studies included in the previous Cochrane review;Searching several electronic databases (Cochrane Library, Medline, Embase,CINAHL, PsychInfo, Amed, SIGLE, HMIC); and Writing to the principal investigatorsof potentially eligible trials. SELECTION CRITERIA: We included in this reviewall randomised trials of screening for colorectal cancer that compared faecaloccult blood test (guaiac or immunochemical) on more than one occasion with noscreening and reported colorectal cancer mortality. DATA COLLECTION ANDANALYSIS: Data from the eligible trials were independently extracted by tworeviewers. The primary data analysis was performed using the group participantswere originally randomised to ('intention to screen'), whether or not theyattended screening; a secondary analysis adjusted for non-attendence. Wecalculated the relative risks and risk differences for each trial, and thenoverall, using fixed and random effects models (including testing forheterogeneity of effects). We identified nine articles concerning fourrandomised controlled trials and two controlled trials involving over 320,000participants with follow-up ranging from 8to 18 years. MAIN RESULTS: Combined results from the 4 eligible randomisedcontrolled trials shows that participants allocated to screening had a 16%reduction in the relative risk of colorectal cancer mortality (RR 0.84, CI:0.78-0.90). In the 3 studies that used biennial screening (Funen, Minnesota, Nottingham)there was a 15% relative risk reduction (RR 0.85, CI: 0.78-0.92) in colorectalcancer mortality. When adjusted for screening attendance in the individualstudies, there was a 25% relative risk reduction (RR 0.75, CI: 0.66 - 0.84) forthose attending at least one round of screening using the faecal occult bloodtest. AUTHORS' CONCLUSIONS: Benefits of screening include a modest reduction incolorectal cancer mortality, a possible reduction in cancer incidence throughthe detection and removal of colorectal adenomas, and potentially, the lessinvasive surgery that earlier treatment of colorectal cancers mayinvolve.Harmful effects of screening include the psycho-social consequences ofreceiving a false-positive result, the potentially significant complications ofcolonoscopy or a false-negative result, the possibility of overdiagnosis(leading to unnecessary investigations or treatment) and the complicationsassociated with treatment.Leggi l'articolo: è full text!