Table 4

Cumulative incidence of colorectal cancer and age-sex-standardised incidence ratios in low-risk patients (n=15 079)

n%No of person-yearsNo of CRCsIncidence rate per 100 000 person-years (95% CI)At 10 yearsP value†Standardisation
No of CRCsCumulative incidence (95% CI)*No of expected CRCs‡SIR (95% CI)
After baseline (without surveillance, censored at any first surveillance visit)
Total15 07910090 451136150 (127 to 178)1131.6% (1.3 to 1.9)1820.75 (0.63 to 0.88)
Sex0.43
 Women67964542 47360141 (110 to 182)451.3% (1.0 to 1.8)680.88 (0.67 to 1.13)
 Men82835547 97876158 (127 to 198)681.8% (1.4 to 2.4)1140.67 (0.52 to 0.83)
Age at baseline, years<0.001
 <5534692322 734731 (15 to 65)40.2% (0.1 to 0.6)110.66 (0.26 to 1.35)
 55−6441932825 2732495 (64 to 142)201.1% (0.7 to 1.7)400.61 (0.39 to 0.90)
 65−7445893026 92664238 (186 to 304)532.3% (1.8 to 3.1)750.85 (0.66 to 1.09)
 ≥7528281915 51841264 (195 to 359)363.0% (2.1 to 4.4)570.72 (0.52 to 0.98)
No of PMPs0.13
 111 7337870 87098138 (113 to 169)791.4% (1.1 to 1.8)1400.70 (0.57 to 0.86)
 221841413 33724180 (121 to 268)201.8% (1.1 to 2.9)290.83 (0.53 to 1.24)
 382754 6459194 (101 to 372)92.9% (1.5 to 5.5)100.86 (0.39 to 1.64)
 433521 6005313 (130 to 751)54.7% (1.7 to 12.9)31.46 (0.47 to 3.40)
PMP size, mm§0.09
 <1010 9857369 586105151 (125 to 183)881.6% (1.3 to 2.0)1400.75 (0.61 to 0.91)
 10−1929812015 65126166 (113 to 244)201.7% (1.0 to 2.8)320.80 (0.53 to 1.18)
 ≥20108675 102478 (29 to 209)41.1% (0.4 to 3.4)100.40 (0.11 to 1.03)
Adenoma histology¶0.22
 Tubular10 3766964 77488136 (110 to 167)761.4% (1.1 to 1.8)1290.68 (0.55 to 0.84)
 Tubulovillous35172318 94434179 (128 to 251)261.9% (1.3 to 3.0)400.85 (0.59 to 1.19)
 Villous35921 8533162 (52 to 502)21.1% (0.2 to 4.5)40.72 (0.15 to 2.10)
 Unknown82754 88011225 (125 to 407)92.7% (1.4 to 5.5)91.23 (0.61 to 2.20)
Adenoma dysplasia**0.79
 Low-grade13 8889284 243125148 (125 to 177)1031.5% (1.3 to 1.9)1690.74 (0.62 to 0.88)
 High-grade74053 3216181 (81 to 402)62.2% (0.9 to 5.5)70.81 (0.30 to 1.77)
 Unknown45132 8875173 (72 to 416)41.7% (0.6 to 5.2)60.86 (0.28 to 2.00)
Proximal polyps††<0.001
 No90916055 86763113 (88 to 144)541.3% (1.0 to 1.8)1080.59 (0.45 to 0.75)
 Yes59884034 58573211 (168 to 266)591.9% (1.5 to 2.5)750.98 (0.77 to 1.23)
After first surveillance (with one or more surveillance visits, censored at end of follow-up)
Total764110062 04570113 (89 to 143)551.1% (0.9 to 1.5)1310.54 (0.42 to 0.68)
Sex0.09
 Women34374528 29839138 (101 to 189)321.6% (1.1 to 2.3)460.85 (0.60 to 1.16)
 Men42045533 7473192 (65 to 131)230.8% (0.5 to 1.2)850.37 (0.25 to 0.52)
Age at baseline, years0.007
 <5520862718 8641369 (40 to 119)100.6% (0.3 to 1.2)140.92 (0.49 to 1.57)
 55−6425003321 25122104 (68 to 157)150.9% (0.5 to 1.6)440.50 (0.31 to 0.76)
 65−7422512917 22125145 (98 to 215)211.7% (1.1 to 2.7)550.46 (0.29 to 0.67)
 ≥7580411471010212 (114 to 395)92.4% (1.1 to 5.1)180.56 (0.27 to 1.03)
No of PMPs0.89
 158937748 68353109 (83 to 143)441.2% (0.9 to 1.6)1010.53 (0.39 to 0.69)
 2109614839611131 (73 to 237)71.0% (0.5 to 2.3)180.60 (0.30 to 1.07)
 3458634644115 (43 to 308)31.0% (0.3 to 3.3)80.50 (0.14 to 1.29)
 4194315022133 (33 to 532)10.7% (0.1 to 5.0)40.54 (0.07 to 1.96)
PMP size, mm§0.43
 <1052336841 13445109 (82 to 147)351.1% (0.8 to 1.6)860.52 (0.38 to 0.70)
 10−1916742214 5191496 (57 to 163)111.0% (0.5 to 1.8)320.44 (0.24 to 0.74)
 ≥207179623011177 (98 to 319)91.9% (1.0 to 3.7)130.85 (0.42 to 1.51)
Adenoma histology¶0.02
 Tubular50166639 8743383 (59 to 116)240.7% (0.5 to 1.1)830.40 (0.27 to 0.56)
 Tubulovillous19562616 19726161 (109 to 236)221.8% (1.1 to 2.7)350.75 (0.49 to 1.09)
 Villous217318602108 (27 to 430)10.7% (0.1 to 5.0)40.45 (0.05 to 1.63)
 Unknown452641159219 (114 to 420)82.7% (1.3 to 5.4)91.03 (0.47 to 1.95)
Adenoma dysplasia**0.71
 Low-grade69129055 21463114 (89 to 146)491.1% (0.8 to 1.5)1160.55 (0.42 to 0.70)
 High-grade46264059374 (24 to 229)30.9% (0.3 to 2.9)90.32 (0.07 to 0.92)
 Unknown267327724144 (54 to 384)31.6% (0.5 to 4.9)60.70 (0.19 to 1.78)
Proximal polyps††0.23
 No46496138 52439101 (74 to 139)311.1% (0.7 to 1.5)780.50 (0.36 to 0.68)
 Yes29923923 52131132 (93 to 187)241.2% (0.8 to 1.9)530.59 (0.40 to 0.83)
  • Low-risk patients were those without any of the following: ≥2 PMPs, of which ≥1 was advanced, ≥5 PMPs or ≥1 large (≥20 mm) non-pedunculated PMP.

  • *Cumulative CRC incidence was estimated using the Kaplan-Meier method.

  • †P values were calculated with the log-rank test to compare cumulative CRC incidence among each category of the specified variable.

  • ‡Numbers of expected CRCs were calculated by multiplying the 5-year age-group and sex-specific observed person-years by the corresponding CRC incidence rates in the general population of England in 2007.

  • §PMP size was defined according to the largest PMP seen at baseline. Patients with PMPs of unknown size are not included in the table; in the analyses without surveillance, there were 27 such patients, of whom one was diagnosed with CRC; and in the analyses with one or more surveillance visits, there were 17 such patients with no CRC cases.

  • ¶Adenoma histology was defined according to the greatest degree of villousness seen at baseline.

  • **Adenoma dysplasia was defined according to the highest grade of dysplasia seen at baseline.

  • ††Proximal polyps were defined as those proximal to the descending colon.

  • CRC, colorectal cancer; PMP, premalignant polyp; SIR, standardised incidence ratio.