Table 2. Univariate Cox logistic regression analysis for both cohorts.
| Characteristics | Training group, no. (%) | Validation group, no. (%) | |||||
|---|---|---|---|---|---|---|---|
| B− (16,812) | B+ (731) | P | B− (8,246) | B+ (365) | P | ||
| Age at diagnosis (year) | <0.0001 | <0.0001 | |||||
| <50 | 394 (2.3) | 41 (5.6) | 152 (1.8) | 16 (4.4) | |||
| 50–70 | 7,695 (45.8) | 395 (54.0) | 3,645 (44.2) | 205 (56.2) | |||
| >70 | 8,723 (51.9) | 295 (40.4) | 4,449 (54.0) | 144 (39.5) | |||
| Gender | 0.584 | 0.660 | |||||
| Male | 10,489 (62.4) | 464 (63.5) | 5,088 (61.7) | 221 (60.5) | |||
| Female | 6,323 (37.6) | 267 (36.5) | 3,158 (38.3) | 144 (39.5) | |||
| Race | 0.198 | 0.013 | |||||
| White | 14,148 (84.2) | 597 (81.7) | 6,885 (83.5) | 285 (78.1) | |||
| Black | 1,856 (11.0) | 94 (12.9) | 930 (11.3) | 59 (16.2) | |||
| Other (American Indian/Alaskan Native, Asian/Pacific Islander) | 808 (4.8) | 40 (5.5) | 431 (5.2) | 21 (5.8) | |||
| Marital status | 0.004 | 0.309 | |||||
| Single | 2,216 (13.2) | 124 (17.0) | 1,197 (14.5) | 62 (17.0) | |||
| Married | 8,461 (50.3) | 372 (50.9) | 4,068 (49.3) | 182 (49.9) | |||
| Other | 6,135 (36.5) | 235 (32.1) | 2,981 (36.2) | 121 (33.2) | |||
| Insurance | 0.008 | 0.004 | |||||
| No | 629 (3.7) | 42 (5.7) | 205 (2.5) | 19 (5.2) | |||
| Yes | 16,183 (96.3) | 689 (94.3) | 8,041 (97.5) | 346 (94.8) | |||
| Grade | <0.0001 | <0.0001 | |||||
| Well differentiated; Grade I | 511 (3.0) | 15 (2.1) | 272 (3.3) | 6 (1.6) | |||
| Poorly differentiated; Grade III | 7,278 (43.3) | 204 (27.9) | 3,580 (43.4) | 114 (31.2) | |||
| Poorly differentiated; Grade III | 8,883 (52.8) | 501 (68.5) | 4,323 (52.4) | 241 (66.0) | |||
| Undifferentiated; Grade IV | 140 (0.8) | 11 (1.5) | 71 (0.9) | 4 (1.1) | |||
| Tumor location | 0.008 | 0.013 | |||||
| Upper lobe | 9,486 (56.4) | 387 (52.9) | 4,620 (56.0) | 197 (54.0) | |||
| Middle lobe | 612 (3.6) | 34 (4.7) | 319 (3.9) | 15 (4.1) | |||
| Lower lobe | 5,009 (29.8) | 208 (28.5) | 2,497 (30.3) | 98 (26.8) | |||
| Main bronchus | 846 (5.0) | 50 (6.8) | 425 (5.2) | 25 (6.8) | |||
| Other sites | 859 (5.1) | 52 (7.1) | 385 (4.7) | 30 (8.2) | |||
| Laterality | 0.024 | 0.003 | |||||
| Left | 7,389 (44.0) | 309 (42.3) | 3,542 (43.0) | 148 (40.5) | |||
| Right | 9,364 (55.7) | 415 (56.8) | 4,669 (56.6) | 211 (57.8) | |||
| Bilateral, single primary | 59 (0.4) | 7 (1.0) | 35 (0.4) | 6 (1.6) | |||
| T stage | <0.0001 | <0.0001 | |||||
| T1 | 3,446 (20.5) | 38 (5.2) | 1,730 (21.0) | 22 (6.0) | |||
| T2 | 6,049 (36.0) | 234 (32.0) | 2,933 (35.6) | 98 (26.8) | |||
| T3 | 3,927 (23.4) | 222 (30.4) | 1,881 (22.8) | 91 (24.9) | |||
| T4 | 3,390 (20.2) | 237 (32.4) | 1,702 (20.6) | 154 (42.2) | |||
| N stage | <0.0001 | <0.0001 | |||||
| N0 | 8,476 (50.4) | 169 (23.1) | 4,273 (51.8) | 76 (20.8) | |||
| N1 | 1,920 (11.4) | 75 (10.3) | 860 (10.4) | 41 (11.2) | |||
| N2 | 5,091 (30.3) | 374 (51.2) | 2,440 (29.6) | 184 (50.4) | |||
| N3 | 1,325 (7.9) | 114 (15.5) | 673 (8.2) | 64 (17.5) | |||
| Number of organs with metastases besides the brain | <0.0001 | <0.0001 | |||||
| 0 | 14,320 (85.2) | 418 (57.2) | 6,985 (84.7) | 185 (50.7) | |||
| 1 | 1,944 (11.5) | 202 (27.6) | 989 (12.0) | 113 (31.0) | |||
| 2 | 473 (2.8) | 85 (11.6) | 233 (2.8) | 50 (13.7) | |||
| 3 | 75 (0.4) | 26 (3.6) | 39 (0.5) | 17 (4.7) | |||
| Bone metastasis | <0.0001 | <0.0001 | |||||
| No | 15,662 (93.2) | 555 (75.9) | 7,654 (92.8) | 269)73.7) | |||
| Yes | 1,150 (6.8) | 176 (24.1) | 592 (7.2) | 96 (26.3) | |||
| Liver metastasis | <0.0001 | <0.0001 | |||||
| No | 16,212 (96.4) | 629 (86.0) | 7,961 (96.5) | 300 (82.2) | |||
| Yes | 600 (3.6) | 102 (14.0) | 285 (3.5) | 65 (17.8) | |||
| Lung metastasis | <0.0001 | <0.0001 | |||||
| No | 15,447 (91.9) | 559 (76.5) | 7,551 (91.6) | 262 (71.8) | |||
| Yes | 1,365 (8.1) | 172 (23.5) | 695 (8.4) | 103 (28.2) | |||
| Chemotherapy | <0.0001 | <0.0001 | |||||
| No | 9,836 (58.5) | 377 (51.6) | 4,771 (57.9) | 174 (47.7) | |||
| Yes | 6,976 (41.5) | 354 (48.4) | 3,475 (42.1) | 191 (52.3) | |||
| Surgery | <0.0001 | <0.0001 | |||||
| No | 10,063 (59.9) | 688 (94.1) | 5,247 (63.6) | 346 (94.8) | |||
| Yes | 6,749 (40.1) | 43 (5.9) | 2,999 (36.4) | 19 (5.2) | |||
| Radiotherapy | <0.0001 | <0.0001 | |||||
| No | 9,794 (58.3) | 180 (24.6) | 4,663 (56.5) | 99 (27.1) | |||
| Yes | 7,018 (41.7) | 551 (75.4) | 3,583 (43.5) | 266 (72.9) | |||
B−, absence of brain metastasis; B+, presence of brain metastasis.