Colonoscopy surveillance for high risk polyps does not always prevent colorectal cancer

Table 1 Clinical and demographic characteristics of patients who developed colorectal cancer at the index AA/TSA/ASSA resection site n (%)

Characteristics	Developed CRC (n = 84)	No CRC (n = 252)	P value1
Demographics
Male sex	56 (66.7)	138 (54.8)	0.06
Age, yr (≥ 70)	40 (47.6)	85 (33.7)	0.02
Time interval from first treatment for advanced adenoma till cancer or last surveillance colonoscopy in years (median, IQR)	4.24 (1.51-7.23)	6.0 (4.05-9.35)	< 0.01
Number of colonoscopies between first polypectomy and cancer (mean ± SD)	1.65 ± 2.30	1.47 ± 1.6	0.83
Adenoma size (1-2 cm)	31 (42.5)	146 (58.2)	0.03
Adenoma size (> 2 cm)	20 (27.4)	27 (10.8)	0.0007
Flat/sessile	76 (91.6)	161 (66.8)	< 0.01
Degree of dysplasia
High grade	28 (33.3)	66 (26.2)	0.18
Low grade/no dysplasia	56 (66.7)	186 (73.8)	0.18
Number of attempts to remove the polyp (mean ± SD)	2.05 ± 1.62	1.26 ± 0.60	< 0.01
Number of polyps resected (> 3 polyps)	14 (16.7)	21 (8.3)	0.03
Polypectomy device used
Hot snare	19 (24.1)	41 (16.3)	0.11
Cold snare	5 (6.3)	26 (10.3)	0.11
Snare NOS	60 (75.9)	185 (73.4)	0.11
Additional treatments
Piecemeal removal	21 (27.6)	30 (13.1)	< 0.01
Mucosal lift	13 (17.1)	23 (10.0)	0.10
Polyp location
Right colon	63 (75.0)	110 (43.7)	< 0.01
Left colon	8 (9.52)	106 (42.1)	< 0.01
Rectum	13 (15.5)	36 (14.3)	< 0.01

¹P-values for continuous variables were obtained using the Kruskal-Wallis Test; Pearson’s χ² test was used for discrete variables. CRC: Colorectal cancer.

Table 2 Risk factors for colorectal cancer at AA/TSA/ASSA resection site

Risk factors	Univariate analysis, HR (95%CI)	P value	Multivariate analysis, HR (95%CI)	P value
Male sex (M:F)	1.74 (1.01-2.98)	0.04	2.87 ( 1.14-6.81)	0.03
Age at polypectomy (≥ 70)	2.51 (1.47-4.27)	< 0.01	2.31 (1.04-5.12)	0.04
Polyp size (≥ 20 mm)	2.60 (1.17-5.78)	0.02	3.70 (1.07-12.77)	0.04
Degree of Dysplasia (High:Low)	1.90 (1.06-3.41)	0.03	2.59 (1.09-6.18)	0.03
Polyp location (Left colon: Right colon)	0.10 (0.04-0.22)	< 0.01	0.09 (0.03-0.29)	< 0.01
Polyp location (Rectum: Right colon)	0.47 (0.22-1.02)	0.06	-	-
Number of polyps resected at polypectomy (> 3 polyps)	2.40 (1.10-5.24)	0.03	5.94 (1.98-17.79)	< 0.01
Polypectomy device used (Hot snare: Cold snare)	1.24 (0.49-3.75)	0.46	-	-
Polyp shape (Flat: Pedunculated)	6.15 (2.67-14.15)	< 0.01	2.79 (0.94-15.23)	0.06
Piecemeal removal (Yes:No)	2.80 (1.44-5.46)	< 0.01	5.42 (1.82-16.20)	0.01
Injection-assisted endoscopic mucosal resection (EMR) (Yes:No)	2.15 (0.98-4.68)	0.06	-	-

EMR: Endoscopic mucosal resection.

Table 3 Clinical and demographic characteristics of patients who developed post-polypectomy colorectal cancer at site distinct from index AA/TSA/ASSA polypectomy n (%)

Characteristics	Patients with post-polypectomy CRC (n = 54)	Patients who did not develop CRC (n = 162)	P value1
Demographics
Male sex	27 (50.0)	88 (54.3)	0.58
Age ≥ 70	26 (48.2)	52 (32.1)	0.04
Time interval from first treatment for advanced adenoma till cancer or last surveillance colonoscopy in years (median, IQR)	5.11 (2.67-10.37)	6.8 (4.0-10.26)	0.08
Number of colonoscopies between first polypectomy and cancer (mean ± SD)	1.24 ± 1.58	1.65±1.68	0.03
Adenoma size (10-20 mm)	25 (48.1)	106 (65.8)	0.03
Adenoma size (≥ 20 mm)	9 (17.3)	20 (12.4)	0.51
Flat/sessile	47 (92.2)	91 (58.71)	< 0.01
Degree of dysplasia
High grade	17 (31.5)	51(31.5)	-
Low grade/no dysplasia	37 (68.5)	111 (68.5)	-
Number of attempts to remove the polyp (mean ± SD)	1.35 ± 0.68	1.33 ± 0.68	< 0.01
Number of polyps resected at polypectomy (> 3 polyps)	11 (20.4)	15 (9.5%)	0.04
Polypectomy Device used
Hot snare	12 (22.2)	26(16.05)	0.63
Cold snare	4 (7.4)	12(7.0)	0.63
Snare NOS	38 (70.5)	127 (76.5)	0.63
Additional treatments
Piecemeal removal	9 (16.7)	21(13.0)	0.5
Injection-assisted EMR	3 (5.6)	16 (10.0)	0.33
Polyp location
Right colon	31 (57.4)	40 (24.7)	< 0.01
Left colon	13 (24.1)	89 (54.9)	< 0.01
Rectum	10 (18.5)	33 (20.4)	< 0.01

¹P-values for continuous variables were obtained using the Kruskal-Wallis Test; Pearson’s chi-square test was used for discrete variables. CRC: Colorectal cancer.

Table 4 Risk factors for post-polypectomy colorectal cancer distinct from index AA/TSA/ASSA site

Risk factors	Univariate analysis, HR (95%CI)	P value	Multivariate analysis, HR (95%CI)	P value
Male sex (M:F)	0.79 (0.40-1.57)	0.50	-	-
Age at polypectomy (≥ 70)	3.68 (1.82-7.48)	< 0.01	3.02 (1.23-7.41)	0.02
Polyp size (≥ 20 mm)	1.93 (0.77-4.83)	0.16	-	-
Degree of dysplasia (High: Low)	1.41 (0.65-3.08)	0.39	-	-
Polyp location (Left colon: Right)	0.15 (0.07-0.34)	< 0.01	0.23 (0.08-0.63)	< 0.01
Polyp location (Rectum:Right colon)	0.22 (0.07-0.68)	< 0.01	0.23 (0.05-1.00)	0.05
Number of polyps resected at polypectomy (> 3 polyps)	2.94 (1.14-7.54)	0.03	4.05 (1.38-11.90)	0.01
Polypectomy device used (Hot snare:Cold snare)	0.64 (0.22-2.34)	0.24	-	-
Polyp shape (Flat/sessile: Pedunculated)	8.0 (2.62-24.05)	< 0.01	3.92 (1.10-14.04)	0.04
Piecemeal removal (Yes:No)	1.68 (0.67-4.22)	0.27	-	-
Injection-assisted EMR (Yes:No)	0.70 (0.19-2.60)	0.59	-	-

EMR: Endoscopic mucosal resection.