Abstract
SummaryBackgroundColorectal cancer is the third most common cancer worldwide. Previous analyses have only reported follow-up after flexible sigmoidoscopy for a maximum of 12 years. We aimed to examine colorectal cancer incidence and mortality after a single flexible sigmoidoscopy screening and 17 years of follow-up.MethodsIn this multicentre randomised trial (UK Flexible Sigmoidoscopy Screening Trial), done between Nov 14, 1994, and March 30, 1999, 170 432 eligible men and women, who had indicated on a previous questionnaire that they would probably attend screening if invited, were randomly assigned (1:2) to an intervention group (offered flexible sigmoidoscopy screening) or a control group (not contacted). Randomisation was done centrally in blocks of 12, and stratified by trial centre, general practice, and household type. The nature of the intervention did not allow the staff to be masked to arm of the trial; however, randomisation was done in batches so that the control group and participants not yet randomised were unaware of their allocation status. The primary outcomes were incidence and mortality of colorectal cancer. Hazard ratios (HRs) and 95% CIs for colorectal cancer incidence and mortality were estimated for intention-to-treat and per-protocol analyses. The trial is registered with ISRCTN, number 28352761.FindingsOur cohort analysis included 170 034 people: 112 936 in the control group and 57 098 in the intervention group, 40 621 (71%) of whom were screened and 16 477 (29%) were not screened. During screening and a median of 17·1 years' follow-up, colorectal cancer was diagnosed in 1230 individuals in the intervention group and 3253 in the control group, and 353 individuals in the intervention group versus 996 individuals in the control group died from colorectal cancer. In intention-to-treat analyses, colorectal cancer incidence was reduced by 26% (HR 0·74 [95% CI 0·70–0·80]; p<0·0001) in the intervention group versus the control group and colorectal cancer mortality was reduced by 30% (0·70 [0·62–0·79]; p<0·0001) in the intervention group versus the control group. In per-protocol analyses, adjusted for non-compliance, colorectal cancer incidence and mortality were 35% (HR 0·65 [95% CI 0·59–0·71]) and 41% (0·59 [0·49–0·70]) lower in the screened group.InterpretationA single flexible sigmoidoscopy continues to provide substantial protection from colorectal cancer diagnosis and death, with protection lasting at least 17 years.FundingNational Institute for Health Research Efficacy and Mechanism Evaluation.
Highlights
The UK Flexible Sigmoidoscopy Screening Trial (UKFSST) is examining the magnitude and duration of effect of a single flexible sigmoidoscopy screening, between ages 55 years and 64 years, on colorectal cancer incidence and mortality
In intention-to-treat analyses, colorectal cancer incidence was reduced by 26% (HR 0·74 [95% CI 0·70–0·80]; p
In per-protocol analyses, adjusted for non-compliance, colorectal cancer incidence and mortality were 35% (HR 0·65 [95% CI 0·59–0·71]) and 41% (0·59 [0·49–0·70]) lower in the screened group
Summary
The UK Flexible Sigmoidoscopy Screening Trial (UKFSST) is examining the magnitude and duration of effect of a single flexible sigmoidoscopy screening, between ages 55 years and 64 years, on colorectal cancer incidence and mortality. Similar findings have since been reported by two further trials examining the effectiveness of a single flexible sigmoidoscopy at 55 years to 64 years, in Italy and Norway, with 11 years of follow-up.[3,4]. On the basis of an independent economic analysis using the UKFSST results, the UK National Screening Committee approved the addition of a single flexible sigmoidoscopy screen at age 55 years to the English Bowel Cancer Screening Programme (BCSP) in 2011.5 The BCSP already included two-yearly guaiac faecal occult blood testing (gFOBT) offered from ages 60 years to 74 years. The aim is for full population coverage to be achieved in 2021; at the time of writing, flexible sigmoidoscopy screening was being offered by 62 (97%) of the 64 BCSP screening centres (National Health Service Bowel Cancer Screening programme, personal communication). In view of www.thelancet.com Vol 389 April 1, 2017
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