Table 1.
Patient demographic and clinical characteristics.
| Unadjusted | sIPTW | PSM | |||||||
|---|---|---|---|---|---|---|---|---|---|
| Characteristic | Palbociclib + letrozole(n=330) | Letrozole(n=221) | Standardized difference | Palbociclib + letrozole(n=321) | Letrozole(n=269) | Standardized difference | Palbociclib + letrozole(n=194) | Letrozole(n=194) | Standardized difference |
| Age, y | |||||||||
| Mean (SD) | 65.7 (10.2) | 70.0 (10.6) | –0.410 | 67.0 (10.4) | 67.7 (11.5) | –0.063 | 66.7 (11.0) | 68.9 (10.6) | –0.201 |
| Median (IQR) | 66.0 (15.0) | 71.0 (18.0) | 67.0 (15.0) | 68.0 (17.0) | 67.0 (17.0) | 69.0 (17.0) | |||
| 18−49 | 24 (7.3) | 10 (4.5) | 0.117 | 20 (6.3) | 14 (5.1) | 0.049 | 16 (8.2) | 10 (5.2) | 0.124 |
| 50−64 | 121 (36.7) | 56 (25.3) | 0.247 | 106 (32.9) | 90 (33.4) | –0.010 | 60 (30.9) | 54 (27.8) | 0.068 |
| 65−74 | 115 (34.8) | 64 (29.0) | 0.127 | 106 (33.0) | 85 (31.7) | 0.027 | 63 (32.5) | 61 (31.4) | 0.022 |
| 75+ | 70 (21.2) | 91 (41.2) | –0.441 | 89 (27.8) | 80 (29.7) | –0.042 | 55 (28.4) | 69 (35.6) | –0.155 |
| Race/ethnicity* | |||||||||
| White | 219 (66.4) | 146 (66.1) | 0.006 | 212 (66.0) | 178 (66.2) | –0.003 | 106 (54.6) | 131 (67.5) | –0.267 |
| Black | 20 (6.1) | 26 (11.8) | –0.201 | 21 (6.4) | 26 (9.7) | –0.122 | 20 (10.3) | 16 (8.2) | 0.071 |
| Asian | 3 (0.9) | 5 (2.3) | –0.109 | 3 (1.0) | 5 (1.9) | –0.080 | 3 (1.5) | 4 (2.1) | –0.039 |
| Hispanic or Latino | 9 (2.7) | 3 (1.4) | 0.097 | 8 (2.5) | 6 (2.0) | 0.032 | 4 (2.1) | 3 (1.5) | 0.039 |
| Other/Unknown | 79 (23.9) | 41 (18.6) | 0.132 | 77 (24.0) | 54 (20.1) | 0.095 | 61 (31.4) | 40 (20.6) | 0.249 |
| Practice type* | |||||||||
| Academic | 17 (5.2) | 8 (3.6) | 0.075 | 15 (4.8) | 10 (3.7) | 0.052 | 8 (4.1) | 7 (3.6) | 0.027 |
| Community | 313 (94.8) | 213 (96.4) | 305 (95.2) | 259 (96.3) | 186 (95.9) | 187 (96.4) | |||
| Insurance type | |||||||||
| Commercial Health Plan + any other | 69 (20.9) | 55 (24.9) | –0.095 | 73 (22.6) | 61 (22.7) | –0.001 | 32 (24.1) | 34 (25.6) | –0.035 |
| Commercial Health Plan |
85 (25.8) | 37 (16.7) | 0.222 | 77 (23.7) | 50 (18.5) | 0.127 | 31 (23.3) | 26 (19.5) | 0.092 |
| Medicare | 12 (3.6) | 13 (5.9) | –0.106 | 16 (5.0) | 13 (4.9) | 0.005 | 5 (3.8) | 4 (3.0) | 0.042 |
| Medicaid | 4 (1.2) | 2 (0.9) | 0.030 | 4 (1.2) | 3 (1.1) | 0.017 | 1 (0.8) | 1 (0.8) | 0 |
| Other payer type | 160 (48.5) | 114 (51.6) | –0.062 | 153 (47.4) | 142 (52.8) | –0.109 | 64 (48.1) | 68 (51.1) | –0.060 |
| Disease stage at diagnosis* | |||||||||
| I | 38 (11.5) | 22 (10.0) | 0.050 | 38 (11.7) | 24 (8.8) | 0.097 | 25 (12.9) | 21 (10.8) | 0.064 |
| II | 86 (26.1) | 42 (19.0) | 0.170 | 79 (24.8) | 56 (20.9) | 0.093 | 37 (19.1) | 39 (20.1) | –0.026 |
| III | 42 (12.7) | 26 (11.8) | 0.029 | 40 (12.4) | 34 (12.6) | –0.005 | 27 (13.9) | 23 (11.9) | 0.062 |
| IV | 122 (37.0) | 90 (40.7) | –0.077 | 118 (36.7) | 112 (41.6) | –0.102 | 70 (31.6) | 78 (40.2) | –0.085 |
| Not documented | 42 (12.7) | 41 (18.6) | –0.161 | 46 (14.4) | 43 (16.0) | –0.047 | 35 (18.0) | 33 (17.0) | 0.027 |
| ECOG performance status* | |||||||||
| 0 | 126 (38.2) | 54 (24.4) | 0.300 | 105 (32.8) | 89 (33.1) | –0.007 | 57 (29.4) | 54 (27.8) | 0.034 |
| 1 | 70 (21.2) | 45 (20.4) | 0.021 | 68 (21.2) | 55 (20.6) | 0.015 | 44 (22.7) | 41 (21.1) | 0.037 |
| 2, 3, or 4 | 18 (5.5) | 34 (15.4) | –0.329 | 25 (7.9) | 30 (11.3) | –0.113 | 18 (9.3) | 22 (11.3) | –0.068 |
| Not documented | 116 (35.2) | 88 (39.8) | –0.097 | 122 (38.1) | 94 (35.0) | 0.064 | 75 (38.7) | 77 (39.7) | –0.021 |
| Brain metastases | 14 (4.2) | 14 (6.3) | –0.094 | 13 (4.1) | 22 (8.2) | –0.170 | 10 (5.2) | 14 (7.2) | –0.086 |
| Time from initial diagnosis to metastatic diagnosis,* y | |||||||||
| De novo | 122 (37.0) | 90 (40.7) | –0.077 | 118 (36.7) | 112 (41.6) | –0.102 | 70 (36.1) | 78 (40.2) | –0.085 |
| ≤1 | 7 (2.1) | 4 (1.8) | 0.022 | 7 (2.0) | 6 (2.1) | –0.002 | 4 (2.1) | 4 (2.1) | 0 |
| >1–≤5 | 47 (14.2) | 25 (11.3) | 0.088 | 47 (14.7) | 30 (11.3) | 0.101 | 24 (12.4) | 23 (11.9) | 0.016 |
| >5 | 154 (46.7) | 102 (46.2) | 0.010 | 149 (46.5) | 121 (45.0) | 0.032 | 96 (49.5) | 89 (45.9) | 0.072 |
| Number of metastatic sites*,† | |||||||||
| 1 | 66 (20.0) | 51 (23.1) | –0.075 | 74 (23.0) | 46 (17.1) | 0.147 | 43 (22.2) | 37 (19.1) | 0.077 |
| 2 | 119 (36.1) | 88 (39.8) | –0.078 | 117 (36.6) | 107 (39.8) | –0.067 | 82 (42.3) | 81 (41.8) | 0.010 |
| 3 | 91 (27.6) | 56 (25.3) | 0.051 | 83 (25.7) | 76 (28.4) | –0.061 | 43 (22.2) | 52 (26.8) | –0.108 |
| 4 | 36 (10.9) | 17 (7.7) | 0.111 | 30 (9.5) | 25 (9.4) | 0.005 | 17 (8.8) | 15 (7.7) | 0.038 |
| ≥5 | 18 (5.5) | 9 (4.1) | 0.065 | 17 (5.2) | 14 (5.2) | –0.003 | 9 (4.6) | 9 (4.6) | 0 |
| Duration of follow-up, mo | |||||||||
| Mean (SD) | 23.6 (12.3) | 21.9 (14.3) | 0.124 | 23.5 (12.3) | 21.6 (15.7) | 0.133 | 23.5 (12.4) | 21.5 (14.5) | 0.145 |
| Median (IQR) | 22.6 (17.3) | 22.1 (21.5) | 22.6 (17.7) | 22.1 (21.2) | 22.3 (17.7) | 20.6 (22.6) | |||
All data are n (%) unless otherwise noted.
The balance in prognostic baseline characteristics was determined using a standardized difference approach, with a standardized difference of ≥0.10, considered indicative of practical significance (19). The total patient population for the different subgroups varied owing to the use of sIPTW. Therefore, the total number for each subgroup may not have equaled the number in the treatment arm (owing to rounding errors or differences in categorization). Percentages were based on the number of patients reported within each subgroup.
ECOG, Eastern Cooperative Oncology Group; IQR, interquartile range; PSM, propensity score matching; sIPTW, stabilized inverse probability treatment weighting.
*Variable used in the propensity score matching model; de novo vs not de novo were used as categories for initial diagnosis to metastatic diagnosis.
†Multiple metastasis at the same site were counted as 1 site.