Published 31 May 2009, doi:10.1136/bmj.b1846
Cite this as: BMJ 2009;338:b1846

Research

Risk of colorectal cancer seven years after flexible sigmoidoscopy screening: randomised controlled trial

¹ Norwegian Colorectal Cancer Prevention (NORCCAP) Centre, Cancer Registry of Norway, Montebello, NO-0310 Oslo, Norway, ² Department of Medicine, Telemark Hospital, NO-3710 Skien, Norway, ³ School of Pharmacy, University of Oslo, NO-0316 Oslo, ⁴ Department of Gastroenterology, Rikshospitalet University Hospital, NO-0027 Oslo

Objective To determine the risk of colorectal cancer after screening with flexible sigmoidoscopy.

Design Randomised controlled trial.

Setting Population based screening in two areas in Norway—city of Oslo and Telemark county (urban and mixed urban and rural populations).

Participants 55 736 men and women aged 55-64 years.

Intervention Once only flexible sigmoidoscopy screening with or without a single round of faecal occult blood testing (n=13 823) compared with no screening (n=41 913).

Main outcome measures Planned end points were cumulative incidence and mortality of colorectal cancer after 5, 10, and 15 years. This first report from the study presents cumulative incidence after 7 years of follow-up and hazard ratio for mortality after 6 years.

Results No difference was found in the 7 year cumulative incidence of colorectal cancer between the screening and control groups (134.5 v 131.9 cases per 100 000 person years). In intention to screen analysis, a trend towards reduced colorectal cancer mortality was found (hazard ratio 0.73, 95% confidence interval 0.47 to 1.13, P=0.16). For attenders compared with controls, a statistically significant reduction in mortality was apparent for both total colorectal cancer (hazard ratio 0.41, 0.21 to 0.82, P=0.011) and rectosigmoidal cancer (0.24, 0.08 to 0.76, P=0.016).

Conclusions A reduction in incidence of colorectal cancer with flexible sigmoidoscopy screening could not be shown after 7 years’ follow-up. Mortality from colorectal cancer was not significantly reduced in the screening group but seemed to be lower for attenders, with a reduction of 59% for any location of colorectal cancer and 76% for rectosigmoidal cancer in per protocol analysis, an analysis prone to selection bias.

Trial registration Clinical trials NCT00119912 [ClinicalTrials.gov] .

© Hoff et al 2009
This is an open-access article distributed under the terms of the Creative Commons Attribution Non-commercial License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

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