Table 3. Subgroup analysis and sensitive analysis on the outcome of disease-free survival.
| No. of Studies | No. of patients | Heterogeneity | Statistical model used | HR (95% CI) | Significance | |
|---|---|---|---|---|---|---|
| Subtype of HNC | ||||||
| 1. HNSCC | 2 | 540 | I2 = 79.1%; P = 0.028 | Random | 0.58 (0.15, 2.30) | P = 0.438 |
| 2. OSCC | 3 | 525 | I2 = 68.5%; P = 0.042 | Random | 1.73 (0.88, 3.42) | P = 0.112 |
| 3. OPSCC | 1 | 133 | NA | Fixed | 1.68 (0.75, 3.76) | P = 0.206 |
| 4. LSCC | 1 | 238 | NA | Fixed | 0.59 (0.35, 1.00) | P = 0.048 |
| 5. NPC | 3 | 382 | I2 = 15.0%; P = 0.308 | Fixed | 1.77 (1.32, 2.37) | P = 0.001 |
| 6. SGC | 1 | 219 | NA | Fixed | 2.29 (1.25, 4.19) | P = 0.007 |
| PD-L1 expression | ||||||
| 1. mRNA | 1 | 517 | NA | Fixed | 1.05 (0.65, 1.45) | P = 0.812 |
| 2. Protein | 10 | 1520 | I2 = 73.8%; P < 0.001 | Random | 1.48 (0.99, 2.20) | P = 0.056 |
| Origin of population | ||||||
| 1. Europe | 4 | 868 | I2 = 75.6%; P = 0.006 | Random | 0.84 (0.44, 1.61) | P = 0.598 |
| 2. Asia | 6 | 952 | I2 = 0.0%; P = 0.463 | Fixed | 1.99 (1.59, 2.48) | P = 0.001 |
| Cut-off value for PD-L1 positive | ||||||
| 1. > 5% positive expression | 3 | 525 | I2 = 68.5%; P = 0.042 | Random | 1.73 (0.88, 3.42) | P = 0.112 |
| 2. H score > 35 | 2 | 278 | I2 = 37.6%; P = 0.206 | Fixed | 1.71 (1.26, 2.32) | P = 0.011 |
| Sample size of studies | ||||||
| 1. < 100 | 2 | 113 | I2 = 88.3%; P = 0.003 | Random | 0.77 (0.10, 6.15) | P = 0.806 |
| 2. > 100 | 9 | 1924 | I2 = 71.7%; P < 0.001 | Random | 1.52 (1.06, 2.17) | P = 0.022 |
| HR estimation | ||||||
| 1. Reported | 6 | 1429 | I2 = 78.6%; P < 0.001 | Random | 1.54 (0.91, 2.60) | P = 0.106 |
| 2. Available data calculated | 5 | 608 | I2 = 70.9%; P = 0.008 | Random | 1.29 (0.73, 2.28) | P = 0.386 |
| HR Calculation | ||||||
| 1. Multivariate analysis | 2 | 437 | I2 = 0.0%; P = 0.719 | Fixed | 2.50 (1.71, 3.65) | P = 0.001 |
| 2. Univariate analysis | 9 | 1600 | I2 = 70.0%; P = 0.001 | Random | 1.23 (0.84, 1.82) | P = 0.289 |
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.