| Screening Strategy for CRC | Effectiveness in Reducing Incidence and Mortality from CRC† | Ability to Detect Cancers | Likelihood of Generating False-Positive Results | Adverse Effects |
|---|---|---|---|---|
| Digital rectal examination | Case-control study found no difference in mortality OR: 0.96 (0.56, 1.7) (8) [Level II—poor] |
Pathology data suggest <10% of CRCs are within reach of examination finger | Unknown | No direct adverse effects known |
| Office FOBT (1 card) |
Unknown | Only 58% of cancers are detected on the first of 3 cards,
suggesting lower sensitivity than 3-card testing (10)
[Level III—fair] |
Little difference compared with 3-card testing (11;12)
[Level 3—poor] |
No direct adverse effects known |
| Home FOBT (3 cards), unrehydrated |
Biennial testing: 2 trials found mortality reductions of:
15% (1%, 26%) (13) and 18% (1%, 32%) (14)
[Level I—good] |
One-time sensitivity 30%-40%.
Unrehydrated FOBT finds about 25% of cancers (9). |
Single test specificity:
96%-98%
5%-10% of patients will require colonoscopy over 10 years of biennial testing (9) [Level III—good] |
No direct adverse effects known |
| Home FOBT (3 cards), rehydrated |
Annual: 33% mortality reduction (13%, 50%); (2) cancer incidence reduction 20% (10%, 30%) (16) Biennial: 21% mortality reduction (3%, 38%); (15) [Level I—good] |
Single test accuracy for cancer=50% (95% CI 30%, 70%);
for advanced neoplasms, 24% (19%, 29%). (17)
Over 13 years, rehydrated FOBT finds 50% of cancers (2) [Level III—good] |
Single test specificity: 90%
Over 10 to 13 years, 38% of patients tested annually and 28% tested biennially with rehydrated FOBT required colonoscopy (2) [Level III—good] |
Inconvenience, adverse effects resulting from followup tests required after positive results |
| Sigmoidoscopy | Small RCT found decreased CRC mortality with screening: RR
0.50 (0.10, 2.72) (18)
Case- control studies suggest 59% mortality reduction within reach of scope (31%, 75%) (3) [Level I—fair] [Level II—good] |
One-time screening detects 68%-78% of advanced neoplasia (17,20)
[Level III—good] |
N/A | <1 in 10,000 perforation rate for diagnostic exams; bleeding
occurs in 2.5% after diagnostic studies, 5.5% after procedures with polypectomy (19) [Level III—good] |
| Combined FOBT and sigmoidoscopy | Nonrandomized trial found 43% mortality reduction
by adding FOBT to rigid sigmoidoscopy:
RR 0.57 (0.56, 1.19) (4) [Level I—fair-poor] |
One-time screening detects 76% of advanced neoplasia
(17)
Increased yield when sigmoidoscopy added to FOBT (21-23) [Level III—good] |
N/A | Sum of adverse effects from each test alone |
| Double contrast barium enema | Unknown | One-time sensitivity for cancer or large polyps: 48% (24%-67%) (24)
[Level III—fair] |
One-time specificity 85% (82%, 88%) (24)
[Level III—fair] |
Perforations: 1 in 25,000 in study with screening and symptomatic
patients (25)
[Level III—poor] |
| Colonoscopy | Case-control study:
CRC mortality: [Level II—fair] |
Sensitivity for large adenomas: >90%; sensitivity for
cancers probably higher (27)
[Level III—good] |
N/A | Diagnostic procedures: perforations: 1/2000 Polypectomy: [Level III—fair-good] |
*CRC, colorectal cancer; FOBT, fecal occult blood test; RCT, randomized controlled trial.
OR, odds ratio; RR, relative risk. Numbers following in parentheses represent 95% CI.
†Evidence grades for each item are in brackets. Level I: evidence from one or more controlled trials; level II: evidence from cohort or case-control studies; level III: evidence from diagnostic accuracy studies or case series. For each level, the investigators have assigned a quality score based on methods described in Harris et al. 2001. (7) N/A=not applicable (see text).