Table 1.
Patient’s characteristics by subgroups
| Overall population | 1st-line CDK4/6i | 2nd-line CDK4/6i | p (comparing difference between groups of 1st and 2nd line CDK 4/6i) | |
|---|---|---|---|---|
| Age | 0.0001 | |||
| 18–49 | 141 (5.1) | 92 (4.2) | 49 (8.2) | |
| 50–64 | 936 (33.8) | 762 (35.1) | 174 (29.0) | |
| 65–74 | 960 (34.6) | 774 (35.7) | 186 (30.9) | |
| 75+ | 734 (26.5) | 542 (25.0) | 192 (31.9) | |
| Total | 2771 (100) | 2170 (100) | 601 (100) | |
| Race/ethnicity | 0.15 | |||
| Asian | 52 (1.9) | 42 (1.9) | 10 (1.7) | |
| Black | 238 (8.6) | 183 (8.4) | 55 (9.2) | |
| Hispanic or Latino | 199 (7.2) | 154 (7.1) | 45 (7.5) | |
| Not documented | 241 (8.7) | 205 (9.4) | 36 (6.0) | |
| Other Race | 216 (7.8) | 163 (7.5) | 53 (8.8) | |
| White | 1825 (65.9) | 1423 (65.6) | 402 (66.9) | |
| Total | 2771 (100) | 2170 (100) | 601 (100) | |
| Heath insurance type at time between diagnosis of metastases and first line treatment | 0.16 | |||
| Commercial/Medicaid | 63 (2.3) | 49 (2.3) | 14 (2.3) | |
| Commercial | 467 (16.9) | 384 (17.7) | 83 (13.8) | |
| Commercial/Other | 266 (9.6) | 212 (9.8) | 54 (9.0) | |
| Medicaid only | 33 (1.2) | 26 (1.2) | 7 (1.2) | |
| Medicare | 372 (13.4) | 280 (12.9) | 92 (15.3) | |
| Medicare/Medicaid | 89 (3.2) | 68 (3.1) | 21 (3.5) | |
| Medicare/other | 1196 (43.2) | 941 (43.4) | 255 (42.4) | |
| None | 285 (10.3) | 210 (9.7) | 75 (12.5) | |
| Total | 2771 (100) | 2170 (100) | 601 (100) | |
| Health Insurance status | 0.04 | |||
| Uninsured/not documented | 285 (10.3) | 210 (9.7) | 75 (12.5) | |
| Insured | 2486 (89.7) | 1960 (90.3) | 526 (87.5) | |
| Total | 2771 (100) | 2170 (100) | 601 (100) | |
| Year starting CDK4/6i | < 0.001 | |||
| 2015 | 148 (5.3) | 126 (5.8) | 22 (3.7) | |
| 2016 | 295 (10.6) | 233 (10.7) | 62 (10.3) | |
| 2017 | 412 (14.9) | 292 (13.5) | 120 (20.0) | |
| 2018 | 509 (18.4) | 398 (18.3) | 111 (18.5) | |
| 2019 | 518 (18.7) | 402 (18.5) | 116 (19.3) | |
| 2020 | 488 (17.6) | 401 (18.5) | 87 (14.7) | |
| 2021 | 398 (14.4) | 318 (14.7) | 80 (13.3) | |
| 2022 | 3 (0.1) | 0 (0) | 3 (0.5) | |
| Total | 2771 (100) | 2170 (100) | 601 (100) | |
| ET backbone | < 0.001 | |||
| Anastrozole | – | 211 (9.7) | 63 (10.5) | |
| Anastrozole, Fulvestrant | – | 6 (0.3) | 26 (4.3) | |
| Exemestane | – | 46 (2.1) | 20 (3.3) | |
| Exemestane, Fulvestrant | – | 6 (0.3) | 4 (0.7) | |
| Fulvestrant | – | 604 (27.8) | 254 (42.3) | |
| Letrozole | – | 1277 (58.9) | 213 (35.4) | |
| Letrozole, Fulvestrant | – | 12 (0.6) | 14 (2.3) | |
| Tamoxifen | – | 7 (0.3) | 1 (0.2) | |
| Tamoxifen, Fulvestrant | – | 1 (0.1) | 6 (1.0) | |
| Total | – | 2170 (100) | 601 (100) | |
| Backbone CDK4/6i | 0.33 | |||
| Abemaciclib | – | 178 (8.2) | 46 (7.7) | |
| Abemaciclib, Ribociclib | – | 2 (0.1) | 1 (0.2) | |
| Palbociclib | – | 1793 (82.6) | 503 (83.7) | |
| Palbociclib, Abemaciclib | – | 24 (1.1) | 1 (0.2) | |
| Palbociclib, Ribociclib | – | 7 (0.3) | 1 (0.2) | |
| Ribociclib | – | 166 (7.7) | 49 (8.2) | |
| Total | – | 2170 (100) | 601 (100) | |
| Duration of time on CDK4/6i mean (SD), months | 18.9 (16.1) | 19.8 (16.4) | 15.2 (14.1) | 0.001 |
| ECOG PS | 0.03 | |||
| 0 | 1179 (48.7) | 959 (50.2) | 220 (43.1) | |
| 1 | 865 (35.7) | 673 (35.2) | 192 (37.6) | |
| 2 | 287 (11.9) | 213 (11.2) | 74 (14.5) | |
| 3, 4 | 89 (3.7) | 65 (3.4) | 24 (4.7) | |
| Not Documented | ||||
| Total | 2420 (100) | 1910 (100) | 510 (100) | |
| Number of recorded comorbidities | 0.17 | |||
| 0 | 1682 (60.7) | 1320 (60.8) | 362 (60.2) | |
| 1 | 808 (29.2) | 638 (29.4) | 170 (28.3) | |
| 2 | 256 (9.2) | 197 (9.1) | 59 (9.8) | |
| 3 | 25 (0.9) | 15 (0.7) | 10 (1.7) | |
| Total | 2771 (100) | 2170 (100) | 601 (100) | |
| Metastases presentation | < 0.001 | |||
| De novo | 925 (33.4) | 779 (35.9) | 146 (24.3) | |
| Relapsed | 1846 (66.6) | 1391 (64.1) | 455 (75.6) | |
| Total | 2771 (100) | 2170 (100) | 601 (100) | |
| Metastases location | 0.2 | |||
| Bone only | 816 (29.4) | 644 (29.7) | 172 (28.6) | |
| Visceral | 650 (23.5) | 522 (24.1) | 128 (21.3) | |
| Non-visceral | 1305 (47.1) | 1004 (46.3) | 301 (50.1) | |
| Total | 2771 (100) | 2170 (100) | 601 (100) | |
| Number of metastatic sites | 0.30 | |||
| 1 | 1066 (38.5) | 845 (38.9) | 221 (36.8) | |
| 2 | 755 (27.2) | 598 (27.6) | 157 (26.1) | |
| 3 | 490 (17.7) | 370 (17.1) | 120 (20.0) | |
| 4 | 275 (9.9) | 208 (9.6) | 67 (11.1) | |
| ≥ 5 | 185 (6.7) | 149 (6.9) | 36 (6.0) | |
| Total | 2771 (100) | 2170 (100) | 601 (100) | |
| Time from initial diagnosis to metastases, n (%), years | 0.0001 | |||
| De novo | 925 (33.4) | 779 (35.9) | 146 (24.3) | |
| ≤ 1 | 78 (2.8) | 56 (2.6) | 22 (3.7) | |
| > 1–5 | 533 (19.2) | 351 (16.2) | 182 (30.3) | |
| > 5 | 1229 (44.4) | 979 (45.1) | 250 (41.6) | |
| Not documented | 6 (0.2) | 5 (0.2) | 1 (0.2) | |
| Total | 2771 (100) | 2170 (100) | 601 (100) |