From: Colorectal Cancer Screening (PDQ®)
PDQ Cancer Information Summaries [Internet].
Bethesda (MD): National Cancer Institute (US); 2002-.
NCBI Bookshelf. A service of the National Library of Medicine, National Institutes of Health.
Table 2. Effect of Screening Intervention on Surrogate Endpoints (e.g., Stage at Diagnosis and Adenoma Detection)
| Screening Intervention | Study Design | Internal Validity | Consistency | Magnitude of Effects on Surrogate Endpoints | External Validity |
|---|---|---|---|---|---|
| Sigmoidoscopy [2 ,3] | Case-control studies | Poor | Fair | About 45% decrease in detection rate of cancers compared with colonoscopy | Poor |
| FOBT/ Sigmoidoscopy [4,5] | Randomized controlled studies | Fair | Poor | No difference in diagnostic yield between sigmoidoscopy + FOBT vs. sigmoidoscopy alone | N/A |
| Barium Enema [6] | Ecologic and descriptive studies | Fair | Poor | Barium enema detects about 30%–50% of cancers detected by colonoscopy | N/A |
| Colonoscopy [7,8] | Ecologic and descriptive studies | Fair | Poor | About 3% of patients with no distal adenomas have advanced proximal neoplasia. There is a threefold increase in this rate in patients with distal adenomas. | N/A |
| CT Colonography [9 -11] | Ecologic and descriptive studies | Fair | Poor | CT colonography may have similar sensitivity to colonoscopy in certain centers | Poor |
| Stool DNA Mutation Tests [12] | Studies in progress | Unknown | Unknown | Unknown | Unknown |
| Immunochemical FOBT | Cross-sectional study in which iFOBT is administered to persons receiving colonoscopy | Good | Good | iFOBT detects >60% and ≤90% of CRCs | N/A |
CRC = colorectal cancer; CT = computed tomography; FOBT = fecal occult blood test; iFOBT = immunochemical fecal occult blood test; N/A = not available.