Cumulative colorectal cancer (CRC) incidence and age-standardised and sex-standardised incidence ratios
| n (%) | Person-years | CRC cases | Incidence per 100 000 person-years (95% CI) | Follow-up | P value | Standardisation | |||||||
| 3 years | 5 years | 10 years | |||||||||||
| CRC cases | Cumulative incidence (95% CI)* | CRC cases | Cumulative incidence (95% CI)* | CRC cases | Cumulative incidence (95% CI)* | Expected CRCs† | SIR (95% CI) | ||||||
| Low-risk group | – | – | – | – | – | – | – | – | – | – | – | – | – |
| After baseline (no surveillance, censored at first surveillance) | – | – | – | – | – | – | – | – | – | – | <0.0001 | – | – |
| Whole risk group | 14 401 (100) | 84 591 | 143 | 169 (143 to 199) | 45 | 0.4% (0.3 to 0.5) | 77 | 0.7% (0.6 to 0.9) | 124 | 1.7% (1.4 to 2.1) | – | 165 | 0.86 (0.73 to 1.02) |
| Lower-risk subgroup‡ | 5235 (36) | 32 903 | 31 | 94 (66 to 134) | 6 | 0.1% (0.1 to 0.3) | 11 | 0.3% (0.2 to 0.5) | 29 | 1.2% (0.8 to 1.7) | – | 60 | 0.51 (0.35 to 0.73) |
| Higher-risk subgroup‡ | 9166 (64) | 51 688 | 112 | 217 (180 to 261) | 39 | 0.5% (0.4 to 0.7) | 66 | 1.0% (0.8 to 1.3) | 95 | 2.1% (1.7 to 2.6) | – | 105 | 1.07 (0.88 to 1.28) |
| After first surveillance (single surveillance visit, censored at second surveillance) | – | – | – | – | – | – | – | – | – | – | 0.0691 | – | – |
| Whole risk group | 7194 (100) | 34 507 | 41 | 119 (87 to 161) | 14 | 0.2% (0.1 to 0.4) | 27 | 0.6% (0.4 to 0.8) | 40 | 1.5% (1.0 to 2.3) | – | 69 | 0.60 (0.43 to 0.81) |
| Lower-risk subgroup‡ | 2431 (34) | 11 410 | 8 | 70 (35 to 140) | 5 | 0.2% (0.1 to 0.6) | 7 | 0.4% (0.2 to 0.8) | 8 | 0.6% (0.2 to 1.4) | – | 21 | 0.38 (0.16 to 0.74) |
| Higher-risk subgroup‡ | 4763 (66) | 23 097 | 33 | 143 (102 to 201) | 9 | 0.2% (0.1 to 0.4) | 20 | 0.7% (0.4 to 1.0) | 32 | 2.0% (1.3 to 3.0) | – | 47 | 0.70 (0.48 to 0.98) |
| After second surveillance (two or more surveillance visits, censored at end of follow-up) | – | – | – | – | – | – | – | – | – | – | 0.90 | – | – |
| Whole risk group | 3235 (100) | 19 805 | 11 | 56 (31 to 100) | 1 | 0.04% (0.01 to 0.3) | 4 | 0.2% (0.1 to 0.5) | 8 | 0.6% (0.3 to 1.3) | – | 42 | 0.26 (0.13 to 0.47) |
| Lower-risk subgroup‡ | 999 (31) | 5472 | 3 | 55 (18 to 170) | 0 | – | 0 | – | 2 | 0.7% (0.2 to 3.0) | – | 10 | 0.29 (0.06 to 0.84) |
| Higher-risk subgroup‡ | 2236 (69) | 14 332 | 8 | 56 (28 to 112) | 1 | 0.1% (0.01 to 0.4) | 4 | 0.3% (0.1 to 0.7) | 6 | 0.6% (0.2 to 1.4) | – | 32 | 0.25 (0.11 to 0.50) |
| Intermediate-risk group | – | – | – | – | – | – | – | – | – | – | – | – | – |
| After baseline (no surveillance, censored at first surveillance) | – | – | – | – | – | – | – | – | – | – | <0.0001 | – | – |
| Whole risk group | 11 852 (100) | 53 927 | 135 | 250 (211 to 296) | 57 | 0.6% (0.5 to 0.8) | 88 | 1.3% (1.0 to 1.6) | 121 | 2.6% (2.1 to 3.3) | – | 117 | 1.16 (0.97 to 1.37) |
| Lower-risk subgroup§ | 4738 (40) | 23 237 | 33 | 142 (101 to 200) | 13 | 0.4% (0.2 to 0.6) | 20 | 0.7% (0.4 to 1.1) | 27 | 1.3% (0.8 to 2.1) | – | 47 | 0.70 (0.48 to 0.99) |
| Higher-risk subgroup§ | 7114 (60) | 30 690 | 102 | 332 (274 to 404) | 44 | 0.8% (0.6 to 1.1) | 68 | 1.7% (1.3 to 2.2) | 94 | 3.7% (2.9 to 4.7) | – | 70 | 1.46 (1.19 to 1.78) |
| After first surveillance (single surveillance visit, censored at second surveillance) | – | – | – | – | – | – | – | – | – | – | 0.0292 | – | – |
| Whole risk group | 7169 (100) | 33 284 | 62 | 186 (145 to 239) | 17 | 0.3% (0.2 to 0.5) | 34 | 0.8% (0.6 to 1.2) | 57 | 2.6% (1.9 to 3.6) | – | 73 | 0.85 (0.65 to 1.08) |
| Lower-risk subgroup§ | 2806 (39) | 13 151 | 16 | 122 (75 to 199) | 3 | 0.1% (0.04 to 0.4) | 8 | 0.5% (0.2 to 1.0) | 15 | 1.9% (1.0 to 3.4) | – | 27 | 0.59 (0.34 to 0.96) |
| Higher-risk subgroup§ | 4363 (61) | 20 133 | 46 | 228 (171 to 305) | 14 | 0.4% (0.2 to 0.7) | 26 | 1.0% (0.7 to 1.5) | 42 | 3.1% (2.2 to 4.5) | – | 46 | 1.00 (0.73 to 1.33) |
| After second surveillance (two or more surveillance visits, censored at end of follow-up) | – | – | – | – | – | – | – | – | – | – | 0.39 | – | – |
| Whole risk group | 3826 (100) | 24 059 | 49 | 204 (154 to 269) | 10 | 0.3% (0.2 to 0.6) | 19 | 0.7% (0.4 to 1.1) | 36 | 2.0% (1.4 to 2.9) | – | 56 | 0.87 (0.65 to 1.16) |
| Lower-risk subgroup§ | 1419 (37) | 8082 | 13 | 161 (93 to 277) | 3 | 0.3% (0.1 to 0.8) | 6 | 0.6% (0.3 to 1.5) | 10 | 1.7% (0.8 to 3.3) | – | 18 | 0.72 (0.38 to 1.22) |
| Higher-risk subgroup§ | 2407 (63) | 15 977 | 36 | 225 (163 to 312) | 7 | 0.3% (0.2 to 0.7) | 13 | 0.7% (0.4 to 1.2) | 26 | 2.2% (1.4 to 3.3) | – | 38 | 0.95 (0.67 to 1.31) |
| High-risk group | – | – | – | – | – | – | – | – | – | – | – | – | – |
| After baseline (no surveillance, censored at first surveillance) | – | – | – | – | – | – | – | – | – | – | 0.0001 | – | – |
| Whole risk group | 2719 (100) | 9243 | 44 | 476 (354 to 640) | 17 | 1.0% (0.6 to 1.7) | 32 | 3.1% (2.1 to 4.4) | 41 | 5.7% (4.0 to 8.3) | – | 23 | 1.91 (1.39 to 2.56) |
| Lower-risk subgroup¶ | 1817 (67) | 6226 | 17 | 273 (170 to 439) | 7 | 0.6% (0.3 to 1.4) | 13 | 1.9% (1.0 to 3.4) | 17 | 3.8% (2.1 to 6.8) | – | 15 | 1.10 (0.64 to 1.76) |
| Higher-risk subgroup¶ | 902 (33) | 3017 | 27 | 895 (614 to 1305) | 10 | 1.9% (1.0 to 3.6) | 19 | 5.6% (3.5 to 9.0) | 24 | 9.9% (6.2 to 15.7) | – | 8 | 3.55 (2.34 to 5.17) |
| After first surveillance (single surveillance visit, censored at second surveillance) | – | – | – | – | – | – | – | – | – | – | 0.0864 | – | – |
| Whole risk group | 1808 (100) | 7144 | 24 | 336 (225 to 501) | 9 | 0.6% (0.3 to 1.2) | 16 | 1.8% (1.1 to 3.1) | 23 | 5.6% (3.1 to 9.8) | – | 18 | 1.34 (0.86 to 1.99) |
| Lower-risk subgroup¶ | 1211 (67) | 4766 | 12 | 252 (143 to 443) | 5 | 0.5% (0.2 to 1.3) | 8 | 1.3% (0.6 to 2.9) | 11 | 4.4% (1.8 to 10.6) | – | 12 | 1.01 (0.52 to 1.76) |
| Higher-risk subgroup¶ | 597 (33) | 2378 | 12 | 505 (287 to 889) | 4 | 0.9% (0.3 to 2.3) | 8 | 2.9% (1.4 to 6.1) | 12 | 7.8% (3.8 to 15.4) | – | 6 | 1.97 (1.02 to 3.44) |
| After second surveillance (two or more surveillance visits, censored at end of follow-up) | – | – | – | – | – | – | – | – | – | – | 0.74 | – | – |
| Whole risk group | 1113 (100) | 6574 | 16 | 243 (149 to 397) | 3 | 0.3% (0.1 to 1.0) | 9 | 1.2% (0.6 to 2.3) | 15 | 2.6% (1.5 to 4.4) | – | 18 | 0.91 (0.52 to 1.47) |
| Lower-risk subgroup¶ | 737 (66) | 4039 | 9 | 223 (116 to 428) | 1 | 0.2% (0.02 to 1.2) | 6 | 1.3% (0.6 to 2.8) | 9 | 2.4% (1.2 to 4.7) | – | 11 | 0.83 (0.38 to 1.58) |
| Higher-risk subgroup¶ | 376 (34) | 2535 | 7 | 276 (132 to 579) | 2 | 0.6% (0.2 to 2.4) | 3 | 1.0% (0.3 to 3.1) | 6 | 2.7% (1.2 to 6.2) | – | 7 | 1.02 (0.41 to 2.09) |
P values calculated with the log-rank test to compare incidence in the lower-risk and higher-risk subgroups of each risk group.
*One minus the Kaplan-Meier estimator of the survival function was used to estimate the cumulative incidence of colorectal cancer.
†Expected numbers of colorectal cancers were calculated by multiplying the sex and 5-year age-group-specific observed person-years by the corresponding incidence rates in the general population of England in 2007.
‡The higher-risk subgroup included patients with an incomplete colonoscopy or colonoscopy of unknown completeness, a tubulovillous or villous adenoma, or proximal polyps at baseline; the lower-risk subgroup included patients with none of these factors.
§The higher-risk subgroup included patients with an incomplete colonoscopy or colonoscopy of unknown completeness, an adenoma with high-grade dysplasia or proximal polyps at baseline; the lower-risk subgroup included patients with none of these factors.
¶The higher-risk subgroup included patients with an incomplete colonoscopy or colonoscopy of unknown completeness or an adenoma with high-grade dysplasia at baseline; the lower-risk subgroup included patients with none of these factors.
SIR, standardised incidence ratio.