Table 1

Baseline characteristics of the patients

	Unadjusted data			Inverse probability weighting adjusted data†			% imputed
Characteristic	Primary surgery (N=263)	Secondary surgery (N=339)	p Value	Primary surgery (N=263)	Secondary surgery (N=339)	p Value	% imputed
*Age (year)‡	71.0	66.0	<0.001	68.6	68.4	0.65	0.2
*Male sex (%)	48	57	0.05	50	52	0.60	–
*Polyp location (%)							–
Right colon	28	11	<0.001	20	18	0.30
Left colon	52	71	<0.001	58	61	0.37
Rectum	20	19	0.86	22	21	0.86
*Polyp size (cm)‡	3.2	2.1	<0.001	2.6	2.6	0.27	8.0
*Sessile morphology (%)	80	48	<0.001	67	64	0.20	3.3
*Differentiation grade (%)							19.8
Low	18	12	0.06	16	16	0.71
Intermediate	74	79	0.17	77	76	0.66
High	8	9	0.80	8	8	0.54
Invasion depth, Haggitt 3/4 or Sm3 (%)	79	63	0.003	82	60	<0.001	31.7
Lymphovascular invasion (%)	37	38	0.48	38	38	0.64	55.3
*Retrieved lymph nodes 10+ (%)	36	34	0.64	34	34	0.76	0.7
*Positive lymph nodes (%)	10	8	0.48	9	9	0.86	–
BMI‡	26.7	27.5	0.12	26.9	27.4	0.48	26.1
ASA score (%)							0.2
ASA 1	27	31	0.34	29	29	0.91
ASA 2	48	52	0.32	49	50	0.78
ASA 3+	25	17	0.02	22	20	0.81
Charlson Comorbidity Index‡	2.7	2.1	<0.001	2.5	2.2	0.10	0.2
Previous abdominal surgery (%)	39	39	0.96	35	39	0.44	–

Presented estimates are based on analyses following multiple imputation of missing data.
†The propensity score used for inverse probability weighting in this table was based on age, sex, polyp location, polyp size, polyp morphology, differentiation grade, number of retrieved lymph nodes and number of positive lymph nodes (indicated by *). p Values comparing adjusted baseline characteristics are based on 2000 bootstrap resamples.
‡Values are means.
ASA, American Society of Anesthesiology; BMI, body mass index.