Table 2 Univariate analysis and multivariate analysis of the overall survival and disease-free survival after IPTW

Overall survival

Preoperative anemia

< 0.001

< 0.001

 No

1 (reference)

1 (reference)

 Yes

1.54 (1.39, 1.70)

1.36 (1.20, 1.55)

Tumor location

 Rectum

1 (reference)

1 (reference)

 Left-side colon

0.92 (0.81, 1.04)

0.182

0.79 (0.69, 0.90)

< 0.001

 Right-side colon

1.09 (0.97, 1.21)

0.141

0.98 (0.83, 1.16)

0.790

 Entire colon

0.39 (0.06, 2.80)

0.352

0.19 (0.02, 1.65)

0.132

 Cannot distinguish left or right-side colon

1.00 (0.66, 1.53)

0.994

0.76 (0.42, 1.36)

0.355

Tumor type

 Adenocarcinoma

1 (reference)

1 (reference)

 Mucoid adenocarcinoma

1.25 (1.09, 1.42)

0.001

1.17 (0.95, 1.45)

0.144

 Signet-ring cell carcinoma

2.98 (2.27, 3.91)

< 0.001

2.69 (1.64, 4.42)

< 0.001

TNM stage

 0–I

1 (reference)

1 (reference)

 II

1.44 (1.20, 1.73)

< 0.001

1.38 (1.13, 1.68)

0.002

 III

3.17 (2.68, 3.74)

< 0.001

3.10 (2.60, 3.70)

< 0.001

 IV

13.75 (11.33, 16.70)

< 0.001

12.96 (10.28, 16.35)

< 0.001

 Unknown

0.89 (0.56, 1.41)

0.609

0.90 (0.56, 1.46)

0.677

Disease-free survival

Preoperative anemia

< 0.001

< 0.001

 No

1 (reference)

1 (reference)

 Yes

1.33 (1.20, 1.47)

1.28 (1.15, 1.43)

Tumor location

 Rectum

1 (reference)

1 (reference)

 Left-side colon

0.93 (0.84, 1.04)

0.209

0.83 (0.74, 0.93)

0.002

 Right-side colon

1.11 (0.97, 1.26)

0.138

0.99 (0.86, 1.14)

0.901

 Entire colon

0.86 (0.26, 2.81)

0.802

0.55 (0.14, 2.12)

0.385

 Cannot distinguish left or right-side colon

0.96 (0.60, 1.53)

0.857

0.85 (0.52, 1.38)

0.506

Tumor type

 Adenocarcinoma

1 (reference)

1 (reference)

 Mucoid adenocarcinoma

1.29 (1.09, 1.54)

0.004

1.17 (0.98, 1.39)

0.090

 Signet-ring cell carcinoma

2.65 (1.68, 4.18)

< 0.001

2.00 (1.27, 3.14)

0.003

TNM stage

 0–I

1 (reference)

1 (reference)

 II

1.40 (1.20, 1.65)

< 0.001

1.36 (1.15, 1.60)

< 0.001

 III

2.87 (2.48, 3.32)

< 0.001

2.75 (2.38, 3.17)

< 0.001

 IV

9.36 (7.58, 11.55)

< 0.001

9.26 (7.49, 11.44)

< 0.001

 Unknown

0.95 (0.65, 1.39)

0.800

0.95 (0.65, 1.39)

0.789