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Table 1 Characteristics of the patients included in the meta-analysis

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

Study Year Country Cancer type Case (n) Age (Median/Mean, years) Tumor stage
(I/II/III/IV)
Follow-up (Median/Mean, months) Study type Method Cut off value Endpoints NOS
Gerald. et al 2006 Austria Colorectal cancer 143 NA 29/24/78/12 51.8a Retrospective IHC High expression: score (5–12)
Low expression: score (0–4)
OS 8
K. et al 2006 Japan Endometrial cancer 80 57.2a 54/10/10/6 71.6b Retrospective IHC High expression: score (4–6)
Low expression: score (0–3)
OS, PFS 8
Rainer. et al 2007 Japan Renal cell carcinoma 55 NA 22/33 NA Retrospective qPCR High expression: Above the 80th percentile OS 6
Ke. et al 2008 China Hepatocellular carcinoma 138 NA NA NA Retrospective IHC High expression: score (5–9)
Low expression: score (0–4)
OS 8
Kazuhiko. et al 2008 Japan Endometrial Cancer 65 57.7a 44/6/9/6 72b Retrospective IHC High expression: score (4–5)
Low expression: score (0–3)
OS, PFS 8
Hiroshi. et al 2009 Japan Osteosarcoma 47 15b 0/47/0/0 67.4b Retrospective IHC High expression: score (4)
Low expression: score (0–3)
OS 7
Tomoko. et al 2010 Japan Cervical cancer 112 NA 67/45/0/0 NA Retrospective IHC High expression: > 50% of tumor cells were stained OS, PFS 7
Jacek. et al 2011 Poland Vulvar squamous cell carcinoma 76 69.5b NA 51.23b Retrospective IHC > 50% of tumor cells were stained with clusters of higher intensity of expression OS 8
Reinhart. et al 2011 Belgium Melanoma 116 52b NA 71b Prospective IHC Almost none/weak versus strong IDO expression OS, PFS 9
Renske. et al 2012 Netherland Endometrial carcinoma 355 64b 196/58/77/44 63.6b Prospective IHC High expression: score (4–6)
Low expression: score (0–3)
DFS 8
Jin. et al 2013 China Laryngeal squamous cell carcinoma 187 52.4b 20/58/88/21 48.56a Retrospective IHC High expression: score (3–4)
Low expression: score (0–2)
OS, DFS 9
Yunlong. et al 2015 China Esophageal squamous cell cancer 196 54b 113(I–II)/83(III–IV) NA Prospective IHC High expression: score (5–12)
Low expression: score (0–4)
OS 8
Maciej. et al 2015 Poland Melanoma 48 56.9b NA 30.3b Retrospective IHC High expression: score > 47.39 Low expression: score ≤ 47.39 OS 6
Ahlem. et al 2016 Tunisia Nasopharyngeal carcinoma 71 NA 10(I–II)/53(III–IV) 30b Prospective IHC High expression: score (4–5)
Low expression: score (0–3)
OS, PFS 7
Hao. et al 2016 China Gastric adenocarcinoma 357 60.3a 80/79/198/0 41b Retrospective IHC With the X-tile software, the cut-off point was 282, 51% patients were separated into the IDO high expression subgroup OS 7
Tao. et al 2017 China Pancreatic cancer 80 NA 10(I–II)/53(III–IV) 40b Prospective IHC High expression: score (> 4)
Low expression: score (≤4)
OS 8
Tvrtko. et al 2017 Croatia Bladder carcinomas 74 65.3a NA NA Prospective qPCR IDO-positive group, in which expression of IDO gene was detected, regardless of the level of expression. OS 7
Daniel. et al 2017 USA Breast cancer 362 NA 278(I–II)/63(III–IV) NA Retrospective IHC Median cut-point was used to stratify IDO1 scores in low and high statuses. OS 8
Lijie. et al 2017 USA Glioblastoma 148 NA NA NA Prospective qPCR IDO1 mRNA levels were stratified into IDO1- low and -high expressing groups based on the determined cutoff values. OS 8
Wenjuan. et al 2018 China Colorectal cancer 95 NA NA NA Retrospective IHC High expression: score (2–3)
Low expression: score (0–1)
OS 7
Yufeng. et al 2018 Taiwan (China) Thymic carcinoma 69 54a 1/3/45/20 46b Retrospective IHC High expression: score (2–3)
Low expression: score (0–1)
OS, PFS 8
Hiroto. et al 2018 Japan Esophageal cancer 182 66.5a 69/63/41/9 NA Retrospective IHC High expression: score (2–3)
Low expression: score (0–1)
RFS 7
Yuki. et al 2018 Japan Esophageal Cancer 305 66a 123/80/102/0 44.4b Prospective IHC (0; no expression, 1; weak expression, 2; moderate expression or 3; strong expression) OS 9
Masaaki. et al 2018 Japan Gastric Cancer 60 67.8a 0/0/60/0 41a Retrospective IHC A total score of greater than 4+ was defined as IDO positive expression OS, DFS 8
Tamkin. et al 2019 Australia Malignant pleural mesothelioma 67 65b NA NA Retrospective IHC Negative
Positive (>  0%)
OS 7
Wenjuan. et al 2019 China Adenosquamous Lung Carcinoma 183 58b 52/41/71/19 NA Retrospective IHC High- and low-expression based on the determined cutoff values. OS 8
Devarati. et al 2019 USA Anal cancer 63 61b 7/24/9/21 (2 unknown) 35b Retrospective IHC Positive (> 50% IDO1 expression) OS 8
Julia. et al 2019 Germany Rectal cancer 91 64b NA NA Retrospective IHC High expression: score (3–6)
Low expression: score (0–2)
OS, DFS 8
Nadia. et al 2019 Tunisia Vulvar squamous cell carcinoma 61 65.61a 29/4/26/2 NA Retrospective IHC High expression: score (3)
Low expression: score (0–2)
OS, DFS 7
Sha. et al 2019 China Esophageal squamous cell carcinoma 158 56b 0/34/124/0 40.2b Retrospective IHC Positive (> 50% IDO1 expression) RFS 8
Yuhshyan. et al 2019 Taiwan (China) Bladder cancer 108 68a 45/43/19/1 45b Retrospective IHC Strongly Positive (> 25% IDO1 expression) OS, PFS 8
  1. Abbreviations: IHC Immunohistochemistry, qPCR Quantitative Real Time Polymerase Chain Reaction, NOS Newcastle-Ottawa Scale, OS overall survival, DFS disease free survival, PFS progression free survival. a Mean, b Median. NA: Not Available