Demographic and Clinical Characteristics of Study Cohort
| Total (n = 162) | Training (n = 81) | Validation (n = 81) | P | |
| Median age (y) | 62.4 (SD, 9.8) | 64.3 (SD, 11.2) | 62.0 (SD, 8.2) | 0.138 |
| Sex (n) | 1.0 | |||
| Male | 149 (92.0%) | 74 (91.4%) | 75 (92.6%) | |
| Female | 13 (8.0%) | 7 (8.6%) | 6 (7.4%) | |
| T category (AJCC 7th ed.) (n) | 0.987 | |||
| T1 | 20 (12.3%) | 10 (12.3%) | 10 (12.3%) | |
| T2 | 58 (35.8%) | 30 (37.0%) | 28 (34.6%) | |
| T3 | 46 (28.4%) | 23 (28.4%) | 23 (28.4%) | |
| T4 | 38 (23.5%) | 18 (22.2%) | 20 (24.7%) | |
| N category (AJCC 7th ed.) (n) | 0.483 | |||
| N0 | 8 (4.9%) | 6 (7.4%) | 2 (2.5%) | |
| N1 | 15 (9.3%) | 7 (8.6%) | 8 (9.9%) | |
| N2 | 125 (77.2%) | 60 (74.1%) | 65 (80.2%) | |
| N3 | 14 (8.6%) | 8 (9.9%) | 6 (7.4%) | |
| Stage (AJCC 7th ed.) (n) | 1.0 | |||
| I | 1 (0.6%) | 1 (1.2%) | 0 (0%) | |
| II | 1 (0.6%) | 0 (0%) | 1 (1.2%) | |
| III | 13 (8.0%) | 7 (8.6%) | 6 (7.4%) | |
| IV | 147 (90.7%) | 73 (90.1%) | 74 (91.4%) | |
| p16 status (HPV) (n) | 0.812 | |||
| + | 142 (87.7%) | 70 (86.4%) | 72 (88.%9) | |
| − | 20 (12.3%) | 11 (13.6%) | 9 (11.1%) | |
| Smoking history (n) | 1.0 | |||
| >10 pack-years | 60 (37.0%) | 30 (37.0%) | 30 (37.0%) | |
| ≤10 pack-years | 102 (63.0%) | 51 (63.0%) | 51 (63.0%) | |
| PFS (n) | 1.0 | |||
| No | 37 (22.8%) | 18 (22.2%) | 19 (23.5%) | |
| Yes | 125 (77.2%) | 63 (77.8%) | 62 (76.5%) | |
| Median follow-up (y) | 2.1 (SD, 1.3) | 2.1 (SD, 1.4) | 2.1 (SD, 1.3) | 1.0 |
| 2-y PFS (n) | 1.0 | |||
| No | 32 (19.8%) | 16 (19.8%) | 16 (19.8%) | |
| Yes | 130 (80.2%) | 65 (80.2%) | 65 (80.2%) |