Table 1.
General information of included studies.
| First author (year) | Country | Sample size | Age | Tumor type | Detection method | No. of PD-L1 positive (%) | Cut-off value of PD-L1 | Outcome | NOS |
| Aghajani (2017)[17] | Australia | 75 | 51 (24–83) | PTC | IHC | 50 (66.7%) | Allred scores >1 | DFS | 7 |
| Shi (2017)[27] | China | 260 | 46.6 (14–80) | PTC | IHC | 136 (52.3%) | Staining score ≥6 | RFS | 7 |
| Shi (2019)[28] | China | 201 | 49 (12–80) | MTC | IHC | 29 (14.4%) | CPS ≥1 | SRFS | 6 |
| Ahn (2017)[19] | Korea | 407 | 43.8 (16–81) | PTC, FTC, PDTC, ATC | IHC | 27 (6.6%) | ≥1% threshold | DFS | 6 |
| Chintakuntlawar (2017)[23] | USA | 16 | 58 (37–83) | ATC | IHC | 6 (37.5%) | Tumor cells >33% | DFS, OS | 8 |
| Zhou (2019)[29] | China | 85 | NM | FTC | IHC | 57 (67.1%) | NM | NM | 5 |
| Cunha (2013)[25] | Brazil | 293 | 43.6 | DTC | IHC | 244 (83.3%) | Allred scores ≥1 | DFS | 6 |
| Chowdhury1∗ (2016)[24] | Canada | 185 | 45 (18–85) | PTC | IHC | 123 (66.5%) | Cytoplasm score ≥4.5 | DFS | 7 |
| Chowdhury2∗ (2016)[24] | Canada | 185 | 45 (18–85) | PTC | IHC | 74 (40.0%) | Plasma membrane score ≥2.1 | DFS | 7 |
| Aghajani1∗ (2019)[18] | Australia | 101 | 47.0 (20–80) | PTC | IHC | 60 (59.4%) | Serum sPD-L1 ≥0.37 ng/mL | NM | 7 |
| Aghajani2∗ (2019)[18] | Australia | 101 | 47.0 (20–80) | PTC | IHC | 61 (60.4%) | Plasma sPD-L1 ≥0.19 ng/mL | DFS | 7 |
| Aghajani3∗ (2019)[18] | Australia | 101 | 47.0 (20–80) | PTC | IHC | 49 (48.5%) | Serum sPD-L1 ≥0.48 ng/mL | NM | 7 |
| Aghajani4∗ (2019)[18] | Australia | 101 | 47.0 (20–80) | PTC | IHC | 61 (60.4%) | Plasma sPD-L1 ≥0.21 ng/mL | NM | 7 |
| Rosenbaum (2018)[26] | USA | 28 | 64.9 (14–86) | PDTC | IHC | 7 (25.0%) | H-score threshold ≥5 | DFS, OS | 6 |
| Bi (2019)[22] | China | 87 | 47 (21–73) | MTC | IHC | 19 (21.8%) | >1% threshold | DFS, OS | 6 |
| Bai (2017)[21] | China | 126 | NM | PTC | IHC | 67 (53.2%) | Diffuse cytoplasmic staining | NM | 6 |
| Bai (2018)[20] | China | 110 | NM | PTC | IHC | 51 (46%) | Diffuse cytoplasmic staining | NM | 6 |
ATC = anaplastic thyroid carcinoma, DTC = differentiated thyroid carcinoma, FTC = follicular thyroid carcinoma, IHC = immunohistochemistry, MTC = medullary thyroid carcinoma, NM = not-mentioned, PDTC = poorly differentiated thyroid carcinoma, PTC = papillary thyroid cancer, RFS = recurrence-free survival, SRFS = structural recurrence-free survival.
∗
Chowdhury 2016[24] includes 2 studies (Chowdhury1 2016, Chowdhury2 2016) according to the cut-off value for PD-L1 in the cytoplasm and membrane, and Aghajani 2019[18] includes 4 (Aghajani1 2019, Aghajani2 2019, Aghajani3 2019, Aghajani4 2019) studies according to the cut-off value for PD-L1 in the serum and plasma.