Table 1 Baseline characteristics of the patients
|  | Training set (N = 166) | Internal validation set (N = 73) | External validation set (N = 66) |
|---|---|---|---|
Sex | |||
 Male | 67 (40.4%) | 32 (43.8%) | 34 (51.5%) |
 Female | 99 (59.6%) | 41 (56.2%) | 32 (48.5%) |
Age, years | |||
 Median (Interquartile range) | 49.0 (39.0–57.0) | 47.0 (37.0–55.0) | 49.0 (36.0–57.0) |
Symptom number* | |||
 0 | 117 (70.5%) | 46 (63.0%) | 47 (71.2%) |
 1 | 32 (19.3%) | 17 (23.3%) | 14 (21.2%) |
 2 | 10 (6.0%) | 7 (9.6%) | 3 (4.5%) |
 3 | 7 (4.2%) | 3 (4.1%) | 2 (3.1%) |
Hypertension | |||
 Yes | 80 (48.2%) | 30 (41.1%) | 44 (66.7%) |
 No | 86 (51.8%) | 43 (58.9%) | 22 (23.3%) |
Smoker | |||
 Yes | 22 (13.3%) | 12 (16.4%) | 10 (15.2%) |
 No | 144 (86.7%) | 61 (83.6%) | 56 (84.8%) |
Tumor location | |||
 Left | 89 (52.4%) | 35 (47.9%) | 34 (51.5%) |
 Right | 81 (47.6%) | 38 (52.1%) | 32 (48.5%) |
MRI-determined tumor size, cm** | |||
 Median (Interquartile range) | 3.3 (2.0–4.6) | 3.2 (2.2–5.0) | 2.4 (1.7–4.6) |