Summary of Study Characteristics
| Reference | Country of study | Patients (n) | Age (y) | Cancer subtype |
|---|---|---|---|---|
| Park et al. (23) | South Korea | 73 (48 M, 25 F) | 59 | Various |
| Flygare et al. (15) | Sweden | 40 (32 M, 8 F) | 64 | Oropharyngeal |
| Platzek et al. (16) | Germany | 38 (30 M, 8 F) | 63 | Various |
| Cebeci et al. (24) | Turkey | 44 (37 M, 7 F) | 66 | Various |
| Partovi et al. (22) | United States | 14 (13 M, 1 F) | 55 | Various |
| Loeffelbein et al. (25) | Germany | 33 (21 M, 12 F) | 57 | Various |
| Piao et al. (26) | China | 60 (45 M, 15 F) | 51 | Nasopharyngeal |
| Kubiessa et al. (17) | Germany | 17 (13 M, 4 F) | 60 | Various |
| Kanda et al. (27) | Japan | 30 (24 M, 6 F) | 67 | Various |
| Murtojärvi et al. (28) | Finland | 52 (36 M, 16 F) | 64 | Various |
| Becker et al. (18) | Switzerland | 74 (50 M, 24 F) | 62 | Various |
| Hayashi et al. (19) | Japan | 11 (8 M, 3 F) | 73 | Oropharyngeal |
| Chan et al. (20) | Taiwan | 113 (86 M, 27 F) | 51 | Nasopharyngeal |
| Huang et al. (21) | Taiwan | 27 (26 M, 1 F) | 55 | Buccal SCC |
| Schaarschmidt et al. (29) | Germany | 12 (12 M) | 60 | Various |
SCC = squamous cell carcinoma.