Table 1. Patient Characteristics in the Training and Validation Data Sets.
| Characteristic | Patients, No. (%) | ||
|---|---|---|---|
| Training set (N = 1372) | Internal validation set (N = 672) | External validation set (N = 310) | |
| Age, median (IQR), y | 45.0 (38.0-52.0) | 45.0 (37.0-54.0) | 47.0 (40.0-56.0) |
| Sex | |||
| Women | 374 (27.3) | 179 (26.6) | 92 (29.7) |
| Men | 998 (72.7) | 493 (73.4) | 218 (70.3) |
| BMI, median (IQR) | 20.9 (19.1-23.2) | 20.6 (19.0-23.3) | 20.4 (17.9-22.9) |
| Smoking | |||
| No | 880 (64.1) | 447 (66.5) | 273 (88.1) |
| Yes | 492 (35.9) | 225 (33.5) | 37 (11.9) |
| Histology | |||
| Type II | 30 (2.2) | 18 (2.7) | 8 (2.6) |
| Type III | 1342 (97.8) | 654 (97.3) | 302 (97.4) |
| Tumor category | |||
| T1 | 104 (7.6) | 34 (5.1) | 40 (12.9) |
| T2 | 184 (13.4) | 94 (14.0) | 80 (25.8) |
| T3 | 732 (53.4) | 363 (54.0) | 98 (31.6) |
| T4 | 352 (25.7) | 181 (26.9) | 92 (29.7) |
| Node category | |||
| N0 | 174 (12.7) | 92 (13.7) | 48 (15.5) |
| N1 | 544 (39.7) | 244 (36.3) | 87 (28.1) |
| N2 | 472 (34.4) | 232 (34.5) | 128 (41.3) |
| N3 | 182 (13.3) | 104 (15.5) | 47 (15.2) |
| Clinical stage | |||
| I | 37 (2.70) | 13 (1.9) | 11 (3.6) |
| II | 132 (9.6) | 60 (8.9) | 44 (14.2) |
| III | 718 (52.3) | 338 (50.3) | 129 (41.6) |
| IVa | 485 (35.3) | 261 (38.8) | 126 (40.6) |
| Treatment | |||
| IMRT alone | 177 (12.9) | 60 (8.9) | 45 (14.5) |
| CRT | 1195 (87.1) | 612 (91.1) | 265 (85.5) |
| EBV DNA status | |||
| Negative | 557 (40.6) | 265 (39.4) | 194 (62.6) |
| Positive | 815 (59.4) | 407 (60.6) | 116 (37.4) |
| Censored patients | 1117 (81.4) | 551 (82.0) | 223 (71.9) |
| Progression events | 255 (18.6) | 121 (18.0) | 87 (28.1) |
| Death events | 130 (9.5) | 71 (10.6) | 68 (21.9) |
Abbreviations: CRT, chemoradiotherapy; BMI, body mass index (calculated as weight in kilograms divided by height in meters squared); EBV, Epstein-Barr virus; IMRT, intensity-modulated radiation therapy; IQR, interquartile range.