Table 1.

Indirect evidence that screening is likely to reduce CRC mortality

Disease stageMost screen-detected CRCs are localized. Five-year survival following resection of localized CRC ≈90% (17)
Adenomatous polypsMost CRCs develop from benign adenomatous polyps (syn. colorectal adenomas, CRA). Expected CRC mortality is substantially reduced in patients who have undergone polypectomy (ablation of CRAs; ref. 18)
FOBT (RCT)Annual gFOBT reduced cumulative incidence ratio of CRC to 0.80 compared with control (19)
Rigid sigmoidoscopy (case-control study)Odds ratio of death from cancer of the rectum or distal colon was 0.3 in patients who had undergone screening rigid sigmoidoscopy compared with controls (20)