Table 1. Potential sources of heterogeneity of histologic en bloc (R0) resection rate among 60 studies of patients that underwent colorectal endoscopic submucosal dissection.

Variable	Studies, n	Tumors, n	R0 resection rate (95 % CI), %	P value1
Type of article				0.23
Full-text journal	41	6006	84 (80, 87)
Abstract	19	2306	81 (72, 87)
Study design				0.04
Retrospective	36	6738	85 (81, 88)
Prospective	7	531	75 (62, 85)
Setting				0.11
Single center	49	6876	84 (80, 87)
Multicenter	4	1079	73 (58, 83)
Start year of data collection				0.31
< 2005	14	1586	77 (70, 83)
2005 – 2009	30	4835	85 (81, 88)
≥ 2010	11	826	86 (71, 93)
Continent				0.004
Asia	40	7392	87 (84, 90)
Europe	16	806	70 (62, 77)
South America (Brazil)	2	18	83 (59, 95)
North America (USA)	2	96	65 (55, 73)
Average age, years2				0.47
≤ 64	14	1798	84 (77, 88)
65 – 67	14	3563	82 (77, 87)
> 67	14	1444	87 (78, 93)
Female, %2				0.33
≤ 36	15	1613	84 (79, 88)
37 – 43	14	2172	88 (81, 93)
≥ 44	14	2066	80 (72, 86)
Number of tumors2				0.71
< 40	20	418	86 (78, 91)
40 – 90	20	1291	80 (73, 86)
> 90	20	6603	84 (79, 88)
Average tumor size, mm2				0.09
≤ 27	16	1844	85 (81, 89)
28 – 34	16	2409	85 (78, 90)
≥ 34	16	2061	80 (70, 88)
Histology
Carcinoid	7	221	85 (79, 89)	0.19
Non-carcinoid	48	5051	82 (78, 86)
Length of the procedure, min§				0.009
≤ 61	15	2141	89 (84, 93)
62 – 101	15	2954	84 (79, 88)
> 101	15	1564	78 (68, 85)

N, number; R0, histologic en bloc resection rate

¹Potential sources of heterogeneity was assessed with metaregression. P < 0.05 indicates that the variable significantly explains part of the between study heterogeneity (i. e. an effect mofier). Differences in continent, lenth of the procedure, study design and average tumor size explains 18 %, 15 %, 8 %, and 4 % of the heterogeneity respectively.

²Indicates variables that were cut at tertiles in order to ensure comparability of number of studies between groups.