General Characteristics of Study Participants (n = 658)
| Characteristic | n | % | PET group (n = 136) | NO-PET group (n = 522) | P |
| Age (y) | 1.000 | ||||
| ≤40 | 112 | 17 | 23 (17) | 89 (17) | |
| >40 | 546 | 83 | 113 (83) | 433 (83) | |
| Treatment modality | 1.000 | ||||
| Surgery | 17 | 2 | 3 (2) | 14 (3) | |
| Surgery + radiotherapy/CCRT | 641 | 98 | 133 (98) | 508 (97) | |
| Pathologic T status | 0.203 | ||||
| pT1–3 | 394 | 60 | 88 (65) | 306 (59) | |
| pT4 | 264 | 40 | 48 (35) | 216 (41) | |
| Pathologic N status | 0.110 | ||||
| N0 | 237 | 36 | 57 (42) | 180 (35) | |
| N+ | 421 | 64 | 79 (58) | 342(65) | |
| Pathologic stage | 0.123 | ||||
| p stage I–III | 214 | 32 | 52 (38) | 162 (31) | |
| p stage IV | 444 | 68 | 84 (62) | 360 (69) | |
| Tumor depth (mm) | 0.528 | ||||
| <10 | 196 | 30 | 37 (27) | 159 (31) | |
| ≥10 | 462 | 70 | 99 (73) | 363 (69) | |
| Margin status (mm) | 0.007 | ||||
| ≤4 | 87 | 13 | 28 (21) | 59 (11) | |
| >4 | 571 | 87 | 108 (79) | 463 (89) | |
| Extracapsular spread | 0.061 | ||||
| No | 397 | 60 | 92 (68) | 305 (58) | |
| Yes | 261 | 40 | 44 (32) | 217 (42) | |
| Cell differentiation | 0.194 | ||||
| Well/moderate | 574 | 87 | 114 (84) | 460 (88) | |
| Poor | 84 | 13 | 22 (16) | 62 (12) | |
| Perineural invasion | 0.001 | ||||
| No | 342 | 52 | 53 (39) | 289 (55) | |
| Yes | 316 | 48 | 83 (61) | 233 (45) | |
| Vascular invasion | 0.018 | ||||
| No | 634 | 96 | 126 (93) | 508 (97) | |
| Yes | 24 | 4 | 10 (7) | 14 (3) | |
| Lymphatic invasion | 0.236 | ||||
| No | 607 | 92 | 128 (94) | 479 (92) | |
| Yes | 51 | 8 | 8 (6) | 43 (8) | |
| Changes in treatment protocol* | 0.456 | ||||
| No | 580 | 88 | 123 (90) | 457 (88) | |
| Yes | 78 | 12 | 13 (10) | 65 (12) |
↵* Treatment protocol was not followed as originally planned.
Data in parentheses are percentages.