How effective are flexible sigmoidoscopy and guaiac-based FOBT in screening for CRC?
Four trials compared FOBT to no screening and 5 trials compared flexible sigmoidoscopy to no screening. No studies compared the 2 methods directly. To show an effect of CRC screening on all-cause mortality, a very large number of individuals would need to be included; the present studies were underpowered regarding this endpoint. An evaluation of costs of screening was beyond the scope of this review.
CRC is the third most frequent cancer in the world. As the asymptomatic period is several years and a good prognosis is associated with early-stage diagnosis, screening has been implemented in many countries. Screening with FOBT and flexible sigmoidoscopy have been shown to reduce mortality from CRC in RCTs. Their comparative effectiveness on CRC mortality has, however, not been evaluated previously.