Impact of colorectal cancer screening participation in remote northern Canada: A retrospective cohort study

Table 1 Adenoma and colorectal cancer classification

Classification	Description
LRA	One to three tubular adenomas or sessile serrated adenomas that are each < 10 mm diameter
HRA	Three or more tubular adenomas or an AA described as having at least one of the following features: Size > 10 mm diameter, villous or tubulovillous histology, and/or high-grade dysplasia
AN	Either an AA or cancer
CRC	Cancer identified including early stage (I and II), and late stage (III and IV)

These definitions are in keeping with the United States Multi-Society Task Force colorectal cancer guidelines for colonoscopy surveillance after screening and polypectomy[36,37]. LRA: Low risk adenoma; HRA: High risk adenoma; AN: Advanced neoplasia; CRC: Colorectal cancer; AA: Advanced adenoma.

Table 2 Screen detected vs clinically detected cancer, 2014-2016

Baseline characteristics	Screen detected (n = 19)	Clinically detected (n = 34)	P value
Age, mean years (SD)	63.2 (7.47)	59.1 (7.27)	0.061
Sex, female (%; Std. Res)	6 (31.58; -0.56)	15 (68.42; 0.45)	0.37
Indigenous (%; Std. Res)	11 (33.33; -0.24)	22 (66.66; 0.18)	0.62
Region of residence (%; Std. Res)			0.892
Beaufort Delta	< 5 (21.05; -0.31)	9 (26.47; 0.23)
Dehcho	N/A	N/A
Fort Smith	< 5 (5.26; -0.59)	< 5 (11.76; 0.44)
Hay River	< 5 (15.79; 0.31)	< 5 (11.76; -0.23)
Sahtu	< 5 (0; -0.85)	< 5 (5.88; 0.63)
Tilcho	< 5 (10.53; 0.16)	< 5 (8.82; -0.12)
Yellowknife	9 (47.37; 0.54)	12 (35.29; -0.40)
Histology type, n (%; Std. Res)			0.132
Adenocarcinoma	18 (94.74; 0.37)	28 (82.35; -0.28)
Carcinoid	< 5 (5.26; 1.07)	< 5 (0; -0.80)
Mucinous	< 5 (0; -0.85)	< 5 (5.88; 0.63)
Other	< 5 (0; -1.20)	< 5 (11.76; 0.90)
Location, n (%; Std. Res)			0.252
Proximal	< 5 (10.53; -1.23)	11 (32.35; 0.92)
Distal	17 (89.47; 0.70)	23 (67.65; -0.53)
Stage, n (%; Std. Res)			0.18
Early	12 (63.16; 0.75)	15 (44.12; -0.56)
Late	7 (36.83; -0.76)	19 (55.88; 0.57)

¹Mann-Whitney-Wilcoxon Test.

²Fisher’s Exact Test for Count Data. Std. Res: Standardized residual. N/A: Not applicable.

Table 3 Demographics and outcomes of screen eligible vs symptomatic individuals

Baseline characteristics	FIT eligible (n = 390)	Symptomatic (n = 288)	P value
Age, mean years (SD)	60.15 (6.55)	61.18 (6.82)	0.04741
Sex, female, n (%; Std. Res)	157 (40.26; -0.52)	127 (44.10; 0.58)	0.316
Indigenous, n (%; Std. Res)	152 (38.97; -2.15)	162 (56.25; 2.49)	0.000008
Region of residence, n (%; Std. Res)			0.0092
Beaufort Delta	42 (10.77; -0.26)	34 (11.81; 0.30)
Dehcho	17 (4.36; -0.58)	17 (5.90; 0.67)
Fort Smith	26 (6.67; -1.62)	36 (12.50; 1.88)
Hay River	39 (10.00; -0.80)	38 (13.19; 0.93)
Sahtu	21 (5.38; 0.06)	15 (5.21; -0.08)
Tilcho	18 (4.62; -0.94)	21 (7.29; 1.09)
Yellowknife	227 (58.20; 1.64)	127 (44.10; -1.91)
Size of health centre, n (%; Std. Res)			0.0002
Yellowknife	219 (56.15; 1.94)	115(39.93; -2.26)
Regional
Fort Smith	26 (6.67; -1.62)	36 (12.50; 1.88)
Hay River	36 (9.23; -0.84)	36 (12.50; 0.98)
Inuvik	21(5.38; 0.60)	11(3.82; -0.70)
Small community	88 (22.56; -1.42)	90 (31.25; 1.66)
Colonoscopy, n (%)	333 (85.38)	212 (74.65)	0.29
Completed, n (%; Std. Res)	318 (95.50; 0.15)	198 (93.40; -0.19)
Incomplete, n (%; Std. Res)	15 (4.50; -0.65)	14 (6.60; 0.81)
FIT to colonoscopy, d
Mean	159.9	183.4	0.011
Median	149.0	199.5	0.02
< 60 d, n (%; Std. Res)	79 (23.87; 0.88)	38 (18.10; -1.10)
60-180 d, n (%; Std. Res)	111 (33.53; 0.69)	59 (28.10; -0.86)	0.04
> 180 d, n (%; Std. Res)	141 (42.60; -1.16)	113 (53.80; 1.45)	0.011
Findings, n (%; Std. Res)
Low risk adenoma	99 (29.73; 1.17)	45 (21.23; -1.47)	0.03
High risk adenoma	130 (39.03; 1.41)	58 (27.36; -1.77)	0.005
Advanced adenoma	65 (19.52; 0.18)	39 (18.40; -0.23)	0.75
Cancer	13 (3.90; -1.60)	20 (9.43; 2.00)	0.008
Advanced neoplasia	78 (23.42; -0.62)	59 (27.83; 0.78)	0.25

¹Welch two sample t-test.

²Not specific to region. Std. Res: Standardized residual; SD: Standard deviation; FIT: Fecal immunohistochemical test.