Table 2.
Incident Colorectal Cancer after No Lower Endoscopy, Negative Lower Endoscopy, or Polypectomy.*
| Variable | No Lower Endoscopy | Polypectomy | Negative Sigmoidoscopy | Negative Colonoscopy |
|---|---|---|---|---|
| All participants | ||||
| No. of person-yr | 980,154 | 72,375 | 381,093 | 304,774 |
| No. of cases of colorectal cancer | 1164 | 82 | 348 | 221 |
| Age-adjusted incidence rate† | 45.7 | 31.4 | 19.3 | 14.1 |
| Age-adjusted hazard ratio (95% CI) | 1.00 | 0.60 (0.47–0.76) | 0.59 (0.52–0.66) | 0.44 (0.37–0.51) |
| Multivariate hazard ratio (95% CI)‡ | 1.00 | 0.57 (0.45–0.72) | 0.60 (0.53–0.68) | 0.44 (0.38–0.52) |
| Disease stage§ | ||||
| I or II | ||||
| No. of cases | 484 | 38 | 143 | 89 |
| Age-adjusted hazard ratio (95% CI) | 1.00 | 0.68 (0.48–0.96) | 0.57 (0.47–0.69) | 0.42 (0.32–0.54) |
| Multivariate hazard ratio (95% CI)‡ | 1.00 | 0.62 (0.44–0.88) | 0.57 (0.47–0.70) | 0.41 (0.32–0.53) |
| III | ||||
| No. of cases | 253 | 12 | 72 | 41 |
| Age-adjusted hazard ratio (95% CI) | 1.00 | 0.43 (0.23–0.81) | 0.59 (0.45–0.77) | 0.40 (0.28–0.58) |
| Multivariate hazard ratio (95% CI)‡ | 1.00 | 0.43 (0.23–0.80) | 0.62 (0.47–0.81) | 0.42 (0.29–0.62) |
| IV | ||||
| No. of cases | 159 | 7 | 55 | 26 |
| Age-adjusted hazard ratio (95% CI) | 1.00 | 0.34 (0.15–0.74) | 0.66 (0.48–0.91) | 0.35 (0.22–0.55) |
| Multivariate hazard ratio (95% CI)‡ | 1.00 | 0.34 (0.15–0.75) | 0.70 (0.51–0.97) | 0.36 (0.23–0.58) |
| Tumor location¶ | ||||
| Proximal colon | ||||
| No. of cases | 379 | 40 | 179 | 119 |
| Age-adjusted hazard ratio (95% CI) | 1.00 | 0.88 (0.63–1.25) | 0.90 (0.75–1.08) | 0.72 (0.57–0.92) |
| Multivariate hazard ratio (95% CI)‡ | 1.00 | 0.83 (0.59–1.18) | 0.92 (0.77–1.11) | 0.73 (0.57–0.92) |
| Distal colorectum | ||||
| No. of cases | 650 | 28 | 136 | 61 |
| Age-adjusted hazard ratio (95% CI) | 1.00 | 0.41 (0.28–0.61) | 0.43 (0.35–0.52) | 0.24 (0.18–0.31) |
| Multivariate hazard ratio (95% CI)‡ | 1.00 | 0.40 (0.27–0.59) | 0.44 (0.36–0.53) | 0.24 (0.18–0.32) |
| Men | ||||
| No. of person-yr | 318,287 | 31,455 | 120,016 | 114,284 |
| No. of cases of colorectal cancer | 471 | 38 | 109 | 96 |
| Age-adjusted hazard ratio (95% CI) | 1.00 | 0.55 (0.39–0.78) | 0.47 (0.37–0.58) | 0.46 (0.36–0.58) |
| Multivariate hazard ratio (95% CI)‡ | 1.00 | 0.52 (0.37–0.74) | 0.47 (0.38–0.59) | 0.46 (0.36–0.58) |
| Women | ||||
| No. of person-yr | 661,868 | 40,921 | 261,077 | 190,490 |
| No. of cases of colorectal cancer | 693 | 44 | 239 | 125 |
| Age-adjusted hazard ratio (95% CI) | 1.00 | 0.63 (0.46–0.86) | 0.66 (0.57–0.77) | 0.42 (0.34–0.52) |
| Multivariate hazard ratio (95% CI)‡ | 1.00 | 0.61 (0.44–0.83) | 0.69 (0.59–0.81) | 0.43 (0.35–0.54) |
Endoscopy status was assigned on the basis of the biennial questionnaire that was returned before a diagnosis of colorectal cancer, death from any cause, or the end of follow-up, whichever came first. Negative sigmoidoscopy and negative colonoscopy were defined as lower endoscopy without detection of an adenoma.
Age-adjusted incidence rates (per 100,000 person-years) were standardized to the age distribution of the population.
Models were further adjusted for body-mass index (<25.0 vs. 25.0–29.9 vs. ≥30.0), smoking status (never smoked vs. former smoker vs. current smoker), status with respect to a history of colorectal cancer in a first-degree relative, status with respect to regular use of aspirin, physical activity level (quintiles of mean METs per week), red-meat intake (quintiles of servings per day), total caloric intake (quintiles of kilocalories per day), alcohol intake (0 or quartiles of grams per day), folate intake (quintiles of micrograms per day), calcium intake (quintiles of milligrams per day), and status with respect to current multivitamin use, nonsteroidal antiinflammatory drug use, cholesterol-lowering drug use, and postmenopausal hormone use (for women only).
Data on disease stage were available for 1379 of 1815 participants (76%): 896 participants who had not undergone lower endoscopy, 57 who had undergone polypectomy, 270 who had negative findings on sigmoidoscopy, and 156 who had negative findings on colonoscopy.
Data on tumor location were available for 1592 of 1815 participants (88%): 1029 participants who had not undergone lower endoscopy, 68 who had undergone polypectomy, 315 who had negative findings on sigmoidoscopy, and 180 who had negative findings on colonoscopy.