Table 1.
Baseline characteristics of the training and validation cohorts.
| Characteristic | Training cohort | External validation cohort | p-value | |
|---|---|---|---|---|
| n = 1,022 (%) | n = 298 (%) | |||
| Age (years) | Median (range) | 66 (33–86) | 66 (25–85) | 0.387 |
| Gender | Male | 666 (65.2) | 195 (65.4) | 0.931 |
| Female | 356 (34.8) | 103 (34.6) | ||
| Smoking history | Never | 461 (45.7) | 132 (45.2) | 0.884 |
| Former/current | 548 (54.3) | 160 (54.8) | ||
| ECOG | 0 | 503 (49.2) | 157 (52.7) | 0.292 |
| performance status | 1 | 519 (50.8) | 141 (47.3) | |
| CEA | ng/mL | 2.1 (1.0–230.1) | 1.9 (1.0–1070.9) | 0.428 |
| WBC | 106/L | 7,399 ± 3.8 | 7,611 ± 3.3 | 0.381 |
| Neutrophil | % | 59.7 ± 31.1 | 60.0 ± 12.4 | 0.722 |
| lymphocyte | % | 29.9 ± 18.7 | 28.5 ± 10.9 | 0.227 |
| Haemoglobin | g/dL | 13.2 ± 3.8 | 13.0 ± 1.7 | 0.518 |
| Platelet | 109/L | 237 ± 79 | 239 ± 83 | 0.610 |
| C-reactive protein | mg/dL | 0.14 (0.0–34.1) | 0.12 (0.02–23.6) | 0.450 |
| Pulmonary function | FEV1 (L) | 2.4 (0.08–352.0) | 2.37 (0.96–139.0) | 0.915 |
| DLCo (%) | 85 (8–173) | 83 (9–159) | 0.327 | |
| Histology | Adenocarcinoma | 651 (63.7) | 2003 (67.1) | 0.442 |
| Squamous | 303 (29.6) | 77 (25.8) | ||
| others | 68 (6.7) | 21 (7.0) | ||
| Tumour size | cm | 2.5 (0.4–13.0) | 2.5 (0.3–13.0) | 0.226 |
| No. of LN positivity | 0 (0–23) | 0 (0-31) | 0.847 | |
| T stage | T1 | 474 (46.5) | 160 (53.7) | 0.064 |
| T2 | 433 (42.5) | 114 (38.3) | ||
| T3/4 | 113 (11.1) | 24 (8.1) | ||
| N stage | N0 | 757 (74.9) | 239 (80.5) | 0.136 |
| N1 | 135 (13.4) | 30 (10.1) | ||
| N2 | 119 (11.8) | 28 (9.4) | ||
| TNM stage | I | 669 (65.7) | 211 (71.0) | 0.218 |
| II | 200 (19.6) | 50 (16.8) | ||
| III | 150 (14.7) | 36 (12.1) | ||
| Tumor differentiation | Well | 197 (19.7) | 75 (25.6) | 0.054 |
| Moderately | 603 (60.4) | 156 (53.2) | ||
| Poorly | 199 (19.9) | 62 (21.1) | ||
| Vascular invasion | Yes | 143 (14.0) | 35 (11.9) | 0.489 |
| Lymphatic invasion | Yes | 353 (34.6) | 95 (32.0) | 0.560 |
| Perineural invasion | Yes | 59 (5.8) | 13 (4.4) | 0.642 |
| Resection status* | R0 | 980 (97.5) | 289 (98.0) | 0.849 |
| R1 | 19 (1.9) | 5 (1.7) | ||
| R2 | 6 (0.6) | 1 (0.3) | ||
| Neoadjuvant treatment | Yes | 50 (4.9) | 14 (4.7) | 0.888 |
| Adjuvant treatment | Yes | 333 (33.1) | 86 (29.3) | 0.214 |
| Recurrence | Yes | 272 (26.6) | 76 (25.2) | 0.618 |
ECOG, Eastern Cooperative Oncology Group; CEA, carcinoembryonic antigen; WBC, white blood cell; FEV1, forced expiratory volume in the first second; DLCo, diffusing capacity of the lung for carbon monoxide; LN, lymph node.
*R0, number of cancer cells seen microscopically at the resection margin; R1, microscopic positive margin; R2, macroscopic positive margin.