n (%) | Person-years | CRC cases | Incidence per 100 000 person-years (95% CI) | Effect of surveillance* | ||
Univariable HR (95% CI) | P value | |||||
Low-risk group | ||||||
Whole risk group | – | – | – | – | – | <0.0001 |
0 visits | 7207 (50.1) | 84 591 | 143 | 169 (143 to 199) | 1 | – |
1 visit | 3959 (27.5) | 34 507 | 41 | 119 (87 to 161) | 0.55 (0.39 to 0.79) | – |
≥2 visits | 3235 (22.5) | 19 805 | 11 | 56 (31 to 100) | 0.23 (0.12 to 0.44) | – |
Total | 14 401 (100) | 138 903 | 195 | 140 (122 to 162) | – | – |
Lower-risk subgroup† | – | – | – | – | – | 0.15 |
0 visits | 2804 (53.6) | 32 903 | 31 | 94 (66 to 134) | 1 | – |
1 visit | 1432 (27.4) | 11 410 | 8 | 70 (35 to 140) | 0.54 (0.25 to 1.20) | – |
≥2 visits | 999 (19.1) | 5472 | 3 | 55 (18 to 170) | 0.42 (0.12 to 1.48) | – |
Total | 5235 (36.4) | 49 785 | 42 | 84 (62 to 114) | – | – |
Higher-risk subgroup† | – | – | – | – | – | <0.0001 |
0 visits | 4403 (48.0) | 51 688 | 112 | 217 (180 to 261) | 1 | – |
1 visit | 2527 (27.6) | 23 097 | 33 | 143 (102 to 201) | 0.52 (0.35 to 0.78) | – |
≥2 visits | 2236 (24.4) | 14 332 | 8 | 56 (28 to 112) | 0.18 (0.08 to 0.37) | – |
Total | 9166 (63.6) | 89 118 | 153 | 172 (147 to 201) | – | – |
Intermediate-risk group | ||||||
Whole risk group | – | – | – | – | – | 0.0001 |
0 visits | 4683 (39.5) | 53 927 | 135 | 250 (211 to 296) | 1 | – |
1 visit | 3343 (28.2) | 33 284 | 62 | 186 (145 to 239) | 0.58 (0.42 to 0.79) | – |
≥2 visits | 3826 (32.3) | 24 059 | 49 | 204 (154 to 269) | 0.50 (0.34 to 0.73) | – |
Total | 11 852 (100) | 111 270 | 246 | 221 (195 to 251) | – | – |
Lower-risk subgroup‡ | – | – | – | – | – | 0.30 |
0 visits | 1932 (40.8) | 23 237 | 33 | 142 (101 to 200) | 1 | – |
1 visit | 1387 (29.3) | 13 151 | 16 | 122 (75 to 199) | 0.66 (0.35 to 1.23) | – |
≥2 visits | 1419 (30.0) | 8082 | 13 | 161 (93 to 277) | 0.63 (0.31 to 1.29) | – |
Total | 4738 (40.0) | 44 470 | 62 | 139 (109 to 179) | – | – |
Higher-risk subgroup‡ | – | – | – | – | – | 0.0001 |
0 visits | 2751 (38.7) | 30 690 | 102 | 332 (274 to 404) | 1 | – |
1 visit | 1956 (27.5) | 20 133 | 46 | 228 (171 to 305) | 0.53 (0.37 to 0.76) | – |
≥2 visits | 2407 (33.8) | 15 977 | 36 | 225 (163 to 312) | 0.42 (0.27 to 0.65) | – |
Total | 7114 (60.0) | 66 800 | 184 | 275 (238 to 318) | – | – |
High-risk group | ||||||
Whole risk group | – | – | – | – | – | 0.0006 |
0 visits | 911 (33.5) | 9243 | 44 | 476 (354 to 640) | 1 | – |
1 visit | 695 (25.6) | 7144 | 24 | 336 (225 to 501) | 0.51 (0.30 to 0.85) | – |
≥2 visits | 1113 (40.9) | 6574 | 16 | 243 (149 to 397) | 0.32 (0.17 to 0.60) | – |
Total | 2719 (100) | 22 961 | 84 | 366 (295 to 453) | – | – |
Lower-risk subgroup§ | – | – | – | – | – | 0.26 |
0 visits | 606 (33.4) | 6226 | 17 | 273 (170 to 439) | 1 | – |
1 visit | 474 (26.1) | 4766 | 12 | 252 (143 to 443) | 0.66 (0.31 to 1.41) | – |
≥2 visits | 737 (40.6) | 4039 | 9 | 223 (116 to 428) | 0.49 (0.20 to 1.18) | – |
Total | 1817 (66.8) | 15 032 | 38 | 253 (184 to 347) | – | – |
Higher-risk subgroup§ | – | – | – | – | – | 0.0006 |
0 visits | 305 (33.8) | 3017 | 27 | 895 (614 to 1305) | 1 | – |
1 visit | 221 (24.5) | 2378 | 12 | 505 (287 to 889) | 0.41 (0.20 to 0.82) | – |
≥2 visits | 376 (41.7) | 2535 | 7 | 276 (132 to 579) | 0.21 (0.08 to 0.51) | – |
Total | 902 (33.2) | 7929 | 46 | 580 (435 to 775) | – | – |
P values calculated with the likelihood ratio test.
*The number of surveillance visits was included as a time-varying covariate; patients who attended any surveillance contributed person-years to more than one category of number of surveillance visits.
†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.