Table 1. Demographics of the study population.
| Variable | Number of patients (%) |
|---|---|
| Age (year), median (25th of 75th percentile) | 67 (60 to 72)* |
| Sex | |
| Female | 335 (35.3) |
| Male | 614 (64.7) |
| Smoking | |
| Never smoker | 429 (45.2) |
| Current or former smoker | 520 (54.8) |
| History of malignancy other than lung cancer | |
| Absent | 815 (85.9) |
| Present | 134 (14.1) |
| Stage | |
| IA | 467 (49.2) |
| IB | 231 (24.3) |
| IIA | 65 (6.9) |
| IIB | 186 (19.6) |
| Location | |
| Non-lower lobe | 535 (56.4) |
| Lower lobe | 414 (43.6) |
| Histology | |
| Squamous cell carcinoma | 311 (32.8) |
| Adenocarcinoma | 638 (67.2) |
| Adjuvant treatment | |
| Performed | 259 (27.3) |
| No | 690 (72.7) |
| Surgery method | |
| Lobectomy | 890 (93.8) |
| Bilobectomy or pneumonectomy | 59 (6.2) |
| Recurrence | |
| No | 755 (79.6) |
| Locoregional recurrence | 69 (7.3) |
| Distant metastasis | 125 (13.1) |
| Death | |
| Alive | 705 (74.3) |
| Death (lung cancer) | 186 (19.6) |
| Death (with a cause other than lung cancer)** | 58 (6.1) |
*, median (25th to 75th percentile); **, patients were classified as censored at the time of death.