Table 2. Subgroup analysis and sensitive analysis on the outcome of overall survival.
| No. of Studies | No. of patients | Heterogeneity | Statistical model used | HR (95% CI) | Significance | |
|---|---|---|---|---|---|---|
| Subtype of HNC | ||||||
| 1. HNSCC | 3 | 722 | I2 = 20.8%; P = 0.285 | Fixed | 1.03 (0.80, 1.33) | P = 0.827 |
| 2. OSCC | 6 | 971 | I2 = 51.4%; P = 0.067 | Random | 1.58 (1.11, 2.25) | P = 0.011 |
| 3. OPSCC | 2 | 314 | I2 = 0.0%; P = 0.637 | Fixed | 1.13 (0.75, 1.71) | P = 0.568 |
| 4. LSCC | 1 | 238 | NA | Fixed | 0.63 (0.39, 1.03) | P = 0.063 |
| 5. NPC | 1 | 104 | NA | Fixed | 1.58 (0.56, 4.51) | P = 0.390 |
| 6. SGC | 1 | 219 | NA | Fixed | 1.31 (0.63, 2.74) | P = 0.474 |
| PD-L1 expression | ||||||
| 1. mRNA | 1 | 517 | NA | Fixed | 1.05 (0.75, 1.35) | P = 0.745 |
| 2. Protein | 13 | 2051 | I2 = 49.5%; P = 0.018 | Random | 1.26 (0.98, 1.62) | P = 0.069 |
| Origin of population | ||||||
| 1. Europe | 4 | 909 | I2 = 70.6%; P = 0.017 | Random | 1.08 (0.66, 1.78) | P = 0.758 |
| 2. Asia | 7 | 1165 | I2 = 19.2%; P = 0.278 | Fixed | 1.38 (1.12, 1.70) | P = 0.003 |
| Cut-off value for PD-L1 positive | ||||||
| 1. > 5% | 7 | 1076 | I2 = 54.8%; P = 0.030 | Random | 1.46 (1.00, 2.14) | P = 0.051 |
| 2. Score > 1 | 2 | 369 | I2 = 0.0%; P = 0.551 | Fixed | 1.17 (0.88, 1.55) | P = 0.285 |
| Sample size of studies | ||||||
| 1. < 100 | 5 | 436 | I2 = 51.6%; P = 0.067 | Random | 1.47 (0.89, 2.44) | P = 0.134 |
| 2. > 100 | 9 | 2132 | I2 = 45.6%; P = 0.065 | Random | 1.15 (0.91, 1.44) | P = 0.251 |
| HR estimation | ||||||
| 1. Reported | 10 | 2035 | I2 = 51.7%; P = 0.023 | Random | 1.21 (0.93, 1.57) | P = 0.148 |
| 2. Available data calculated | 4 | 533 | I2 = 49.0%; P = 0.118 | Random | 1.30 (0.80, 2.12) | P = 0.289 |
| HR Calculation | ||||||
| 1. Multivariate analysis | 3 | 675 | I2 = 84.9%; P = 0.001 | Random | 1.15 (0.50, 2.67) | P = 0.725 |
| 2. Univariate analysis | 12 | 2131 | I2 = 39.2%; P = 0.072 | Random | 1.14 (0.91, 1.43) | P = 0.241 |
HNC, head and neck cancer; HNSCC, head and neck squamous cell carcinoma; OSCC, oral squamous cell carcinoma; OPSCC, oropharyngeal squamous cell carcinoma; LSCC, laryngeal squamous cell carcinoma; NPC, nasopharyngeal carcinoma; SGC, salivary gland carcinoma; PD-L1, programmed cell death ligand 1; HR, hazard ratio; CI, confidence interval; NA, not applicable.