Table 1.
Baseline characteristics of study population.
| Variables | Categories | Patients with cancer (any stage): N (%) | Group A*N (%) | Group B*N (%) | Patients with brain metastases at diagnosis: N (%) | Incidence proportion of brain metastases |
|---|---|---|---|---|---|---|
| Age* | Continuous | 61.84 (13.56) | 50.49 (7.77) | 72.60 (7.96) | - | - |
| Year | 2011 | 59,276 (15.84%) | 29,711 (50.12) | 29,565 (49.88) | 230 (15.96) | 0.39% |
| 2012 | 60,510 (16.17%) | 29,901 (49.41) | 30,609 (50.59) | 206 (14.3) | 0.34% | |
| 2013 | 61,897 (16.54%) | 30,227 (48.83) | 31,670 (51.17) | 258 (17.9) | 0.42% | |
| 2014 | 62,904 (16.81%) | 30,597 (48.64) | 32,307 (51.36) | 255 (17.7) | 0.41% | |
| 2015 | 64,702 (17.29%) | 31,076 (48.03) | 33,626 (51.97) | 271 (18.81) | 0.42% | |
| 2016 | 64,843 (17.33%) | 30,521 (47.07) | 34,322 (52.93) | 221 (15.34) | 0.34% | |
| Race | NHW | 254,330 (67.98%) | 111,033 (43.66) | 143,297 (56.34) | 882 (61.21) | 0.35% |
| NHB | 41,359 (11.05%) | 23,175 (56.03) | 18,184 (43.97) | 262 (18.18) | 0.63% | |
| NHAI/AN | 2,078 (0.56%) | 1,154 (55.53) | 924 (44.47) | 8 (0.56) | 0.38% | |
| NHAPI | 31,764 (8.49%) | 18,884 (59.45) | 12,880 (40.55) | 109 (7.56) | 0.34% | |
| Hispanic | 42,459 (11.35%) | 26,711 (62.91) | 15748 (37.09) | 179 (12.42) | 0.42% | |
| Others | 2,142 (0.57%) | 1,076 (50.23) | 1,066 (49.77) | 1 (0.07) | 0.05% | |
| Region | Northeast | 61,753 (16.51%) | 30,181 (48.87) | 31,572 (51.13) | 265 (18.39) | 0.43% |
| Midwest | 32,796 (8.77%) | 15,234 (46.45) | 17,562 (53.55) | 120 (8.33) | 0.37% | |
| South | 81,533 (21.79%) | 39,795 (48.81) | 41,738 (51.19) | 381 (26.44) | 0.47% | |
| West | 198,050 (52.94%) | 96,823 (48.89) | 101,227 (51.11) | 675 (46.84) | 0.34% | |
| Marital status | Married | 200,221 (53.52%) | 110,259 (55.07) | 89,962 (44.93) | 601 (41.71) | 0.3% |
| Others | 173,911 (46.48%) | 71,774 (41.27) | 102,137 (58.73) | 840 (58.29) | 0.48% | |
| Insurance status | Insured | 316,864 (84.69%) | 146,250 (46.16) | 170,614 (53.84) | 986 (68.42) | 0.31% |
| Others | 57,268 (15.31%) | 35,783 (62.48) | 21,485 (37.52) | 455 (31.58) | 0.79% | |
| Primary tumor site | Central | 18,861 (5.04%) | 7,856 (41.65) | 11,005 (58.35) | 69 (4.79) | 0.37% |
| Upper-inner | 45,492 (12.16%) | 21,983 (48.32) | 23,509 (51.68) | 70 (4.86) | 0.15% | |
| Lower-inner | 20,571 (5.5%) | 9,354 (45.47) | 11,217 (54.53) | 40 (2.78) | 0.19% | |
| Upper-outer | 124,529 (33.28%) | 62,423 (50.13) | 62,106 (49.87) | 285 (19.78) | 0.23% | |
| Lower-outer | 27,880 (7.45%) | 13,788 (49.45) | 14,092 (50.55) | 58 (4.02) | 0.21% | |
| Axillary tail | 2,020 (0.54%) | 1,069 (52.92) | 951 (47.08) | 17 (1.18) | 0.84% | |
| Others | 134,779 (36.02%) | 65,560 (48.64) | 69,219 (51.36) | 902 (62.6) | 0.67% | |
| T-Stage | 1 | 216,452 (57.85%) | 98,866 (45.68) | 117,586 (54.32) | 183 (12.7) | 0.08% |
| 2 | 107,688 (28.78%) | 57,307 (53.22) | 50,381 (46.78) | 305 (21.17) | 0.28% | |
| 3 | 22,452 (6%) | 13,227 (58.91) | 9,225 (41.09) | 172 (11.94) | 0.77% | |
| 4 | 15,481 (4.14%) | 7,254 (46.86) | 8,227 (53.14) | 453 (31.44) | 2.93% | |
| Others | 12,059 (3.22%) | 5,379 (44.61) | 6,680 (55.39) | 328 (22.76) | 2.72% | |
| LNPRate | 0–20% | 221,250 (59.14%) | 106,721 (48.24) | 114,529 (51.76) | 37 (2.57) | 0.02% |
| 21–40% | 23,323 (6.23%) | 13,757 (58.98) | 9,566 (41.02) | 18 (1.25) | 0.08% | |
| 41–60% | 14,493 (3.87%) | 7,976 (55.03) | 6,517 (44.97) | 9 (0.62) | 0.06% | |
| 61–80% | 6,589 (1.76%) | 3,623 (54.99) | 2,966 (45.01) | 13 (0.9) | 0.2% | |
| 81–100% | 45,984 (12.29%) | 26,599 (57.84) | 19,385 (42.16) | 121 (8.4) | 0.26% | |
| Unexamined | 50,291 (13.44%) | 15,926 (31.67) | 34,365 (68.33) | 1,019 (70.71) | 2.03% | |
| Others | 12,202 (3.26%) | 7,431 (60.9) | 4,771 (39.1) | 224 (15.54) | 1.84% | |
| Subtype | HR+/HER2– | 256,413 (68.54%) | 116,506 (45.44) | 139,907 (54.56) | 550 (38.17) | 0.21% |
| HR+/HER2+ | 37,293 (9.97%) | 22,427 (60.14) | 14,866 (39.86) | 214 (14.85) | 0.57% | |
| HR–/HER2+ | 15,779 (4.22%) | 9,620 (60.97) | 6,159 (39.03) | 165 (11.45) | 1.05% | |
| Triple-negative | 38,558 (10.31%) | 21,842 (56.65) | 16,716 (43.35) | 256 (17.77) | 0.66% | |
| Unknown | 26,089 (6.97%) | 11,638 (44.61) | 14,451 (55.39) | 256 (17.77) | 0.98% | |
| Bone metastases | No | 360,946 (96.48%) | 175,577 (48.64) | 185,369 (51.36) | 522 (36.22) | 0.14% |
| Yes | 13,186 (3.52%) | 6,456 (48.96) | 6,730 (51.04) | 919 (63.78) | 6.97% | |
| Liver metastases | No | 369,081 (98.65%) | 179,181 (48.55) | 189,900 (51.45) | 957 (66.41) | 0.26% |
| Yes | 5,051 (1.35%) | 2,852 (56.46) | 2,199 (43.54) | 484 (33.59) | 9.58% | |
| Lung metastases | No | 367,815 (98.31%) | 179,264 (48.74) | 188,551 (51.26) | 759 (52.67) | 0.21% |
| Yes | 6,317 (1.69%) | 2,769 (43.83) | 3,548 (56.17) | 682 (47.33) | 10.8% | |
| Brain metastases | No | 372,691 (99.61%) | 181,258 (48.63) | 191,433 (51.37) | - | - |
| Yes | 1,441 (0.39%) | 775 (53.78) | 666 (46.22) | - | - | |
| Income* | Continuous | 0.66 (0.17) | 0.66 (0.17) | 0.65 (0.17) | - | - |
| Education* | Continuous | 13.66 (5.74) | 13.72 (5.76) | 13.61 (5.72) | - | - |
| Total | - | 374,132 (100) | 182,033 (48.65) | 192,099 (51.35) | 1,441 (100) | 0.38% |
Income*, median household income, increased by per $10 000 annual; Education*, high school education percent, increased by per 10%; NHW, Non-Hispanic White; NHB, Non-Hispanic Black; NHAI/AN, Non-Hispanic American Indian/Alaska Native; NHAPI, Non-Hispanic Asian or Pacific Islander. Continuous variables* are given as mean (standard deviation). Group A*, age ≤ 61; Group B*, age ≥ 62.