Systematic review of the effectiveness of population screening for colorectal cancer

Abstract

Aim: To estimate the effectiveness of colorectal cancer screening with faecal occult blood testing (FOBT), flexible sigmoidoscopy (FS), and combinations of FOBT and FS in preventing colorectal cancer (CRC) deaths.

Method: A systematic review was conducted examining randomised controlled trials (RCTs) published between 1997 and 2004 inclusive. A systematic search of Medline, Embase, Current Contents, and the Cochrane Library was undertaken. Studies that evaluated screening with FOBT, FS or combinations of FOBT and FS, were appraised. A meta-analysis of population-based trials of FOBT was conducted.

Results: Four RCTs were identified that examined FOBT screening. The three trials that investigated guaiac-based FOBT found CRC mortality was reduced in the screening group. In the two population-based trials, the pooled relative risk was 0.86 (95%CI 0.79-0.93). A fourth RCT was identified, with shorter term follow-up, which considered FOBT screening combined with FS compared with FOBT alone. No significant reduction in CRC mortality was reported in this trial.

Conclusion: There is high-quality evidence showing that guaiac-based FOBT screening reduces mortality from CRC. No such evidence exists for screening with FS either alone, or in combination with FOBT, but this should be re-evaluated once data become available from four large ongoing trials.