Table 2

Standardised incidence ratio (SIR) of colorectal cancer after first adenoma removal according to characteristics of patients and adenomas

	Patients with advanced adenomas				Patients with non-advanced adenomas
	Person-years at risk	Observed cases	SIR	95% CI	Person-years at risk	Observed cases	SIR	95% CI
All	12 183	53	2.23	1.67 to 2.92	23 426	26	0.68	0.44 to 0.99
Gender
Men	7070	34	2.08	1.48 to 2.90	13 551	17	0.64	0.40 to 1.03
Women	5113	19	2.59	1.65 to 4.06	9875	9	0.77	0.40 to 1.48
Age (years)
<60	4396	12	3.65	1.88 to 6.37	11 538	3	0.39	0.08 to 1.13
60–79	6848	30	1.75	1.18 to 2.50	10 892	20	0.74	0.45 to 1.15
≥80	940	11	3.32	1.66 to 5.95	995	3	0.84	0.17 to 2.44
Known family history of colorectal cancer
Yes	1324	7	3.76	1.51 to 7.75	2290	2	0.77	0.09 to 2.77
No	10 860	46	2.10	1.54 to 2.81	21 136	24	0.67	0.43 to 1.00
Time period after initial adenoma (months)
12–36	3640	18	2.76	1.64 to 4.37	6274	4	0.44	0.12 to 1.12
36–60	3250	16	2.61	1.49 to 4.24	5803	4	0.44	0.12 to 1.13
60–120	4516	16	1.73	0.99 to 2.80	9193	13	0.81	0.43 to 1.39
Number of adenomas
1	8409	36	2.32	1.62 to 3.21	17 570	20	0.71	0.44 to 1.10
≥2	3774	17	2.07	1.21 to 3.32	5856	6	0.59	0.21 to 1.28
Adenoma location
Proximal only	1121	3	1.26	0.25 to 3.67	4158	5	0.63	0.20 to 1.47
Distal only	6200	24	2.08	1.33 to 3.09	9931	11	0.68	0.34 to 1.22
Rectum only	2634	14	2.85	1.56 to 4.78	7030	9	0.91	0.41 to 1.72
Multiple locations	2127	12	2.58	1.33 to 4.50	2001	1	0.26	0.00 to 1.47