Table 3

Long-term colorectal cancer (CRC) incidence in the high-risk group by baseline characteristics and number of surveillance visits

N (%)Person-yearsCRC casesIncidence per 100 000 person-years (95% CI)Univariable HR (95% CI)P valueMultivariable HR (95% CI)P value
Total2719 (100)22 96184366 (295 to 453)
Number of surveillance visits*0.00190.0009
 0911 (33.5)924344476 (354 to 640)11
 1695 (25.6)714424336 (225 to 501)0.51 (0.30 to 0.85)0.49 (0.29 to 0.82)
 2593 (21.8)401810249 (134 to 463)0.32 (0.16 to 0.67)0.30 (0.15 to 0.62)
 ≥3520 (19.1)25556235 (105 to 523)0.31 (0.12 to 0.78)0.29 (0.11 to 0.73)
Sex0.320.56
 Women799 (29.4)699730429 (300 to 613)11
 Men1920 (70.6)15 96354338 (259 to 442)0.79 (0.51 to 1.24)0.87 (0.56 to 1.37)
Age, years0.01180.0828
 <55283 (10.4)31916188 (84 to 418)11
 55–64750 (27.6)708220282 (182 to 438)1.53 (0.61 to 3.81)1.68 (0.67 to 4.19)
 65–741065 (39.2)873534389 (278 to 545)2.13 (0.89 to 5.09)2.17 (0.91 to 5.19)
 ≥75621 (22.8)395324607 (407 to 906)3.42 (1.39 to 8.42)2.79 (1.13 to 6.89)
Number of adenomas0.490.38
 31227 (45.1)10 57738359 (261 to 494)11
 4557 (20.5)470413276 (160 to 476)0.77 (0.41 to 1.45)0.81 (0.43 to 1.53)
 5454 (16.7)369718487 (307 to 773)1.35 (0.77 to 2.36)1.45 (0.83 to 2.54)
 ≥6481 (17.7)398315377 (227 to 625)1.05 (0.58 to 1.92)1.24 (0.68 to 2.27)
Adenoma size, mm†0.300.69
 <10264 (9.7)23746253 (114 to 562)11
 10–191344 (49.4)11 36136317 (229 to 439)1.25 (0.53 to 2.97)1.08 (0.45 to 2.57)
 ≥201084 (39.9)895141458 (337 to 622)1.82 (0.77 to 4.28)1.41 (0.58 to 3.39)
 Unknown27 (1.0)2751364 (51 to 2585)1.41 (0.17 to 11.76)1.22 (0.14 to 10.31)
Adenoma histology‡0.190.48
 Tubular1038 (38.2)899431345 (242 to 490)11
 Tubulovillous1293 (47.6)10 70136336 (243 to 466)0.99 (0.61 to 1.59)0.89 (0.55 to 1.45)
 Villous328 (12.1)264816604 (370 to 986)1.77 (0.97 to 3.23)1.40 (0.75 to 2.61)
 Unknown60 (2.2)6191162 (23 to 1147)0.47 (0.06 to 3.41)0.54 (0.07 to 4.09)
Adenoma dysplasia‡0.00270.0009
 Low-grade2035 (74.8)17 10951298 (227 to 392)11
 High-grade616 (22.7)508032630 (445 to 891)2.12 (1.36 to 3.30)2.23 (1.43 to 3.47)
 Unknown68 (2.5)7721130 (18 to 919)0.44 (0.06 to 3.21)0.35 (0.05 to 2.57)
Proximal polyps0.960.47
 No663 (24.4)593422371 (244 to 563)11
 Yes2056 (75.6)17 02762364 (284 to 467)0.99 (0.61 to 1.61)1.21 (0.73 to 2.00)
Completeness of colonoscopy0.06120.0438
 Complete2354 (86.6)19 26664332 (260 to 424)11
 Incomplete123 (4.5)10097694 (331 to 1456)1.66 (1.00 to 2.76)1.73 (1.04 to 2.89)
 Unknown242 (8.9)268613484 (281 to 833)
Bowel preparation quality0.890.89
 Excellent or good1119 (41.2)978835358 (257 to 498)11
 Satisfactory411 (15.1)310612386 (219 to 680)1.08 (0.56 to 2.08)1.03 (0.53 to 1.99)
 Poor143 (5.3)9805510 (212 to 1226)1.46 (0.57 to 3.72)1.42 (0.55 to 3.64)
 Unknown1046 (38.5)908632352 (249 to 498)0.99 (0.61 to 1.59)0.95 (0.59 to 1.53)
Year of baseline visit0.410.36
 1984–1999329 (12.1)394810253 (136 to 471)11
 2000–2004874 (32.1)825034412 (294 to 577)1.62 (0.78 to 3.38)1.65 (0.78 to 3.47)
 2005–20101516 (55.8)10 76240372 (273 to 507)1.48 (0.70 to 3.13)1.65 (0.75 to 3.62)
Length of baseline visit0.600.88
 1 day1184 (43.6)10 10633327 (232 to 459)11
 2 days–3 months562 (20.7)455618395 (249 to 627)1.20 (0.68 to 2.14)1.02 (0.57 to 1.82)
 3–6 months442 (16.3)373812321 (182 to 565)0.98 (0.51 to 1.89)0.89 (0.46 to 1.74)
 ≥6 months531 (19.5)456121460 (300 to 706)1.42 (0.82 to 2.45)1.19 (0.67 to 2.10)
  • The final multivariable model contained number of surveillance visits, completeness of colonoscopy and adenoma dysplasia. For these variables, the multivariable HRs were from the final multivariable model and the p values were for inclusion of the variable in the model, calculated with the likelihood ratio test. For the remaining variables, the multivariable HRs were for if the variable was added as an additional variable to the final multivariable model.

  • *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.

  • †Adenoma size was defined according to the largest adenoma seen at baseline.

  • ‡Adenoma histology and dysplasia were defined according to the worst histology (greatest degree of villousness) and worst dysplasia (highest grade) seen at baseline, respectively.