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Table 2 Hazard ratio for the association between IDO overexpression and solid tumors prognosis

From: The prognostic value of IDO expression in solid tumors: a systematic review and meta-analysis

Stratified analysis Effect size NO. of study Cases HR Heterogeneity
Pooled HR (95% CI) P value I2 (%) p value
All studies
 OS OS 28 3457 1.92 (1.52–2.43) < 0.001 81.1 < 0.001
 TTP TTP 14 1815 2.25 (1.58–3.22) < 0.001 54.8 0.007
Study location
 Asia OS 16 2137 2.12 (1.54–2.92) < 0.001 68.5 < 0.001
TTP 9 1121 2.48 (1.74–3.55) < 0.001 11.4 0.342
 Other countries OS 12 1320 1.66 (1.17–2.37) 0.005 82.2 < 0.001
TTP 5 694 1.99 (1.32–2.98) 0.001 14.3 0.323
Detection method
 IHC OS 25 3180 1.86 (1.46–2.38) < 0.001 81.3 < 0.001
TTP 14 1815 2.25 (1.58–3.22) < 0.001 54.8 0.007
 qPCR OS 3 277 2.11 (1.42–3.13) < 0.001 17.7 0.297
Sample size
  < 70 OS 9 535 2.25 (1.31–3.88) 0.003 75.5 < 0.001
TTP 4 255 2.49 (1.51–4.10) < 0.001 0.0 0.72
 70–120 OS 10 903 2.37 (1.42–3.95) 0.001 55.9 0.02
TTP 6 578 2.43 (1.09–5.44) 0.03 72.8 0.003
  > 140 OS 9 2019 1.60 (1.18–2.18) 0.003 75.8 < 0.001
TTP 4 882 1.98 (1.12–3.51) 0.019 63.2 0.043
Study type
 Retrospective OS 21 2807 1.82 (1.39–2.40) < 0.001 81.5 < 0.001
TTP 11 1273 2.32 (1.50–3.60) < 0.001 57.9 0.008
 Prospective OS 7 650 1.98 (1.57–2.49) < 0.001 0 0.6
TTP 3 542 2.09 (1.03–4.23) 0.04 56.2 0.102
Cancer type
 Digestive system tumor OS 10 1528 1.79 (1.38–2.31) < 0.001 40.8 0.085
 Reproductive system tumor OS 6 756 2.39 (1.53–3.72) < 0.001 34.9 0.175
 Bladder cancer OS 2 182 2.90 (1.32–6.15) 0.006 0.0 0.521
 Colorectal cancer OS 2 238 2.32 (1.22–4.42) 0.01 0.0 0.655
 Endometrial cancer OS 2 145 6.64 (1.41–31.27) 0.017 0.0 0.99
 Esophageal cancer OS 2 501 1.76 (1.28–2.43) 0.001 0.0 0.79
 Esophageal cancer TTP 2 340 2.23 (0.91–5.49) 0.081 77.9 0.033
 Gastric Cancer OS 2 417 1.68 (1.22–2.32) 0.001 1.5 0.314
 Melanoma OS 2 164 1.95 (0.45–8.49) 0.376 84.8 0.01
 Vulvar squamous cell carcinoma OS 2 137 2.92 (1.69–5.04) < 0.001 0.0 0.69
Age (Mean/Median)
  < 60 years OS 9 991 2.02 (1.22–3.36) 0.007 83.6 < 0.001
  > 60 years OS 10 1262 1.76 (1.16–2.67) 0.008 68.8 0.001
Follow-up (Median/Mean)
  ≤ 45 months OS 8 1092 1.90 (1.29–2.78) 0.001 79.4 < 0.001
  > 45 months OS 8 783 3.41 (2.41–4.83) < 0.001 0.0 0.97
Study quality
 NOS score > 7 OS 18 2825 2.00 (1.48–2.69) < 0.001 72.6 < 0.001
 NOS score ≤ 7 OS 10 632 1.75 (1.20–1.57) < 0.001 72.4 < 0.001
  1. Abbreviations: HR hazard ratio, CI confidence interval, OS overall survival, TTP time to tumor progression, IHC Immunohistochemistry, qPCR Quantitative Real Time Polymerase Chain Reaction