Incidence of colorectal cancer and advanced polyps by post-polypectomy surveillance interval: Real-world evidence from Thailand

Table 1 Baseline patient and polyp characteristics by risk group

	High-risk (3-year interval)		Low-risk (5-year interval)		P value1
	N = 1678	%	N = 1197	%
Sex					< 0.001
Women	822	49	684	57.1
Men	856	51	513	42.9
Age in years at baseline
mean (SD)	64.8 (9.5)	N/A	62.0 (9.7)	N/A	< 0.001
< 50	92	5.5	117	9.8	< 0.001
50-75	1328	76.1	971	81.1
> 75	258	15.4	109	9.1
Number of polyps					N/A
1-2	556	33.1	1197	100
3-4	636	37.9	0	0
5-10	273	16.3	0	0
> 10	213	12.7	0	0
Size of polyps in mm					N/A
< 10	637	39.5	1046	100
10-19	636	39.5	0	0
≥ 20	339	21	0	0
Adenoma histology					N/A
Tubular	1252	74.6	1197	100
Tubulovillous	2	0.1	0	0
Villous	45	2.7	0	0
Traditional serrated	379	22.6	0	0
Adenoma dysplasia grade					N/A
No/low-to-intermediate	1348	80.3	1196	100
High	330	19.7	0	0

¹Continuous variables were compared using the independent t test; categorical variables were compared using the Fisher exact test. Data are presented as n (%) unless otherwise specified.

N: Total number of patients; N/A: Not applicable.

Table 2 Baseline characteristics of low-risk patients by surveillance interval, N = 1197

	Early		Usual		Late		P value1
	n = 622	%	n = 139	%	n = 436	%
Sex							0.255
Women	350	56.3	73	52.5	261	59.9
Men	272	43.7	66	47.5	175	40.1
Age in years at baseline
mean (SD)	62.5 (10.5)		61.5 (7.9)		61.6 (9.1)		< 0.001
< 50	60	9.7	10	7.2	47	10.8	0.033
50-75	492	79.1	123	88.5	356	81.6
> 75	70	11.2	6	4.3	33	7.6
Number of polyps							N/A
1-2	622	100	139	100	436	100
Size of polyps in mm							N/A
< 10	622	100	139	100	436	100
Adenoma histology							N/A
Tubular	622	100	139	100	436	100
Adenoma dysplasia grade							N/A
No/low-to-intermediate	622	100	139	100	436	100

¹Continuous variables were compared using one-way analysis of variance; categorical variables were compared using the Fisher exact test. Data are presented as n (%) unless otherwise specified. All low-risk patients had 1-2 polyps < 10 mm, tubular adenoma histology, and no/low-to-intermediate dysplasia; therefore, polyp characteristics are uniform across intervals.

N: Total number of patients; n: Number of patients per subgroup; N/A: Not applicable.

Table 3 Baseline characteristics of high-risk patients by surveillance interval, N = 1678

	Early		Usual		Late		P value1
	n = 849	%	n = 201	%	n = 551	%
Sex							0.337
Women	431	50.8	95	47.3	296	47.1
Men	418	49.2	106	52.7	332	52.9
Age in years at baseline
mean (SD)	64.9 (10.2)		65.6 (8.7)		64.3 (8.7)		< 0.001
< 50	52	5.6	6	3	34	6.2	0.001
50-75	708	76.2	162	81.8	458	83.1
> 75	169	18.2	30	15.2	59	10.7
Number of polyps
1-2	373	40.1	54	27.3	129	23.4	< 0.001
3-4	301	32.4	74	37.3	261	47.4
5-9	140	15.1	34	17.2	99	18
≥ 10	115	12.4	36	18.2	62	11.2
Size of polyps in mm							< 0.001
< 10	247	27.9	82	42.3	308	57.9
10-19	361	40.7	90	46.4	185	34.8
≥ 20	278	31.4	22	11.3	39	7.3
Adenoma histology							< 0.001
Tubular	617	66.4	164	82.8	471	85.5
Tubulovillous	1	0.1	0	0	1	0.2
Villous	31	3.4	1	0.5	13	2.3
Traditional serrated	280	30.1	33	16.7	66	12
Adenoma dysplasia grade							< 0.001
No/low-to-intermediate	645	69.4	184	92.9	519	94.2
High	284	30.6	14	7.1	32	5.8

¹Continuous variables were compared using 1-way analysis of variance; categorical variables were compared using the Fisher exact test. Data are presented as n (%) unless otherwise specified.

N: Total number of patients; n: Number of patients per subgroup.

Table 4 Incidence of colorectal cancer by post polypectomy surveillance interval and risk group

Interval	n (N = 2875)	Follow-up time (patient-years)	CRC cases	Incidence rate (cases per 1000 patient-years)	Incidence proportion (%)	OR1	95%CI1	P value1
High-risk (3-year interval) group
Total	1678	4555.09	14	3.07	0.83
Early	929	1131.04	5	4.42	0.54	Reference
Usual	198	590.94	1	1.69	0.51	0.94	0.11-8.07	0.954
Late	551	2833.11	8	2.82	1.45	2.72	0.89-8.36	0.080
Low-risk (5-year interval) group
Total	1197	5261.89	6	1.14	0.50
Early	622	1601.17	1	0.62	0.16	Reference
Usual	139	687.37	0	0.00	0	N/A	N/A	N/A
Late	436	2973.35	5	1.68	1.15	7.20	0.84-61.88	0.072

¹Univariable logistic regression. The early surveillance group served as the reference category. Follow-up time is measured in patient-years.

CI: Confidence interval; CRC: Colorectal cancer; N: Total number of patients; n: Number of patients per subgroup; N/A: Not applicable; OR: Odds ratio.

Table 5 Incidence of colorectal cancer and advanced polyps by post polypectomy surveillance interval and risk group

Interval	n (N = 2875)	Follow-up time (patient-years)	CRC and advanced polyp cases	Incidence rate (cases per 1000 person-years)	Incidence proportion (%)	OR1	95%CI1	P value1
High-risk (3-year interval) group
Total	1678	4555.09	273	59.93	16.27
Early	929	1131.04	143	126.43	15.39	Reference
Usual	198	590.94	34	57.54	17.17	1.14	0.76-1.72	0.532
Late	551	2833.11	96	33.89	17.42	1.16	0.87-1.54	0.305
Late vs usual						1.02	0.66-1.56	0.936
Low-risk (5-year interval) group
Total	1197	5261.89	87	16.53	7.27
Early	622	1601.17	35	21.86	5.63	Reference
Usual	139	687.37	10	14.55	7.19	1.30	0.63-2.69	0.480
Late	436	2973.35	42	14.13	9.63	1.79	1.12-2.85	0.015
Late vs usual						1.38	0.67-2.82	0.384

¹Univariable logistic regression. The early surveillance group served as the reference category unless otherwise specified (late vs usual comparison is also shown). Follow-up time is measured in patient-years.

CI: Confidence interval; CRC: Colorectal cancer; N: Total number of patients; n: Number of patients per subgroup; OR: Odds ratio.