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Table 1 Patient characteristics

From: Comparative effectiveness of first-line palbociclib plus letrozole versus letrozole alone for HR+/HER2− metastatic breast cancer in US real-world clinical practice

  Unadjusted total cohort Cohort after sIPTW
Characteristic Palbociclib + letrozole (n = 772) Letrozole (n = 658) Standardized difference Palbociclib + letrozole (n = 839) Letrozole (n = 698) Standardized difference
Age, y
 Mean (SD) 65.2 (10.4) 69.2 (10.9) − 0.3793 66.8 (11.2) 67.1 (11.1) − 0.0288
 Median (IQR) 66.0 (58.0–73.0) 70.0 (61.0–79.0)   67.0 (59.0–75.0) 68.0 (60.0–76.0)  
Age group*, n (%), y
 18–49 52 (6.7) 30 (4.6) 0.0944 48 (5.8) 38 (5.5) 0.0114
 50–64 304 (39.4) 187 (28.4) 0.2331 288 (34.3) 244 (35.0) − 0.0131
 65–74 262 (33.9) 193 (29.3) 0.0992 265 (31.6) 221 (31.7) − 0.0025
  ≥ 75 154 (19.9) 248 (37.7) − 0.3995 237 (28.3) 194 (27.8) 0.0107
Race/ethnicity*, n (%)
 White 525 (68.0) 446 (67.8) 0.0048 572 (68.1) 470 (67.4) 0.0163
 Black 54 (7.0) 60 (9.1) − 0.0781 62 (7.4) 55 (7.9) − 0.0187
 Asian 13 (1.7) 10 (1.5) 0.0131 15 (1.7) 11 (1.5) 0.0180
 Hispanic or Latino 22 (2.8) 15 (2.3) 0.0361 23 (2.7) 16 (2.3) 0.0264
 Not documented 158 (20.5) 127 (19.3) 0.0292 167 (20.0) 146 (20.9) − 0.0225
Practice type*, n (%)
 Academic 46 (6.0) 31 (4.7) 0.0555 44 (5.2) 36 (5.2) 0.0010
 Community 726 (94.0) 627 (95.3)   795 (94.8) 661 (94.8)  
Disease stage at initial diagnosis*, n (%)
 I 82 (10.6) 79 (12.0) − 0.0437 90 (10.8) 78 (11.2) − 0.0127
 II 187 (24.2) 149 (22.6) 0.0373 198 (23.6) 161 (23.1) 0.0129
 III 109 (14.1) 97 (14.7) − 0.0177 121 (14.4) 101 (14.4) − 0.0017
 IV 321 (41.6) 254 (38.6) 0.0608 338 (40.3) 283 (40.6) − 0.0062
 Not documented 73 (9.5) 79 (12.0) − 0.0825 91 (10.9) 74 (10.7) 0.0069
ECOG PS*, n (%)
 0 293 (38.0) 167 (25.4) 0.2728 271 (32.3) 227 (32.5) − 0.0059
 1 159 (20.6) 134 (20.4) 0.0057 175 (20.9) 144 (20.7) 0.0055
 2, 3, or 4 49 (6.3) 84 (12.8) − 0.2196 82 (9.7) 66 (9.5) 0.0095
 Not documented 271 (35.1) 273 (41.5) − 0.1316 311 (37.1) 260 (37.3) − 0.0047
Visceral disease*,‡, n (%)
 No 442 (57.3) 437 (66.4)   518 (61.8) 429 (61.5)  
 Yes 330 (42.7) 221 (33.6) 0.1894 320 (38.2) 269 (38.5) − 0.0060
Bone-only disease*, n (%)
 No 501 (64.9) 398 (60.5)   530 (63.1) 440 (63.1)  
 Yes 271 (35.1) 260 (39.5) − 0.0913 309 (36.9) 258 (36.9) − 0.0011
Brain metastases, n (%)
 No 753 (97.5) 628 (95.4)   820 (97.7) 656 (94.0)  
 Yes 19 (2.5) 30 (4.6) − 0.1142 19 (2.3) 42 (6.0) − 0.1901
Time from initial Dx to metastatic Dx*, n (%), y
 De novo 321 (41.6) 254 (38.6) 0.0608 338 (40.3) 283 (40.6) − 0.0062
 ≤ 1 19 (2.5) 23 (3.5) − 0.0609 25 (2.9) 21 (3.1) − 0.0070
 > 1–5 123 (15.9) 111 (16.9) − 0.0253 133 (15.9) 111 (16.0) − 0.0016
 > 5 308 (39.9) 269 (40.9) − 0.0201 342 (40.7) 281 (40.3) 0.0097
 Not documented 1 (0.1) 1 (0.2) − 0.0060 1 (0.1) 1 (0.1) 0.0010
Number of metastatic sites*, n (%)
 1 372 (48.2) 365 (55.5) − 0.1462 423 (50.4) 355 (50.9) − 0.0104
 2 220 (28.5) 147 (22.3) 0.1418 217 (25.9) 183 (26.2) − 0.0070
 3 110 (14.2) 64 (9.7) 0.1396 101 (12.0) 86 (12.4) − 0.0104
 4 40 (5.2) 18 (2.7) 0.1257 35 (4.2) 27 (3.8) 0.0184
 ≥ 5 20 (2.6) 10 (1.5) 0.0755 18 (2.2) 15 (2.2) 0.0002
 Not documented 10 (1.3) 54 (8.2) −0.3293 44 (5.3) 31 (4.5) 0.0371
  1. The balance in important prognostic baseline characteristics was assessed using a standardized difference approach, with a standardized difference of ≥ 0.10 considered indicative of practical significance [24]. The total patient population for different subgroups varied due to the application of sIPTW. Therefore, the total n number for each subgroup may not have always equaled the N number of the treatment arm (due to rounding error and categorization differences). Calculated percentages were based on the number of patients reported within each subgroup
  2. Dx diagnosis, ECOG PS Eastern Cooperative Oncology Group performance status, IQR interquartile range, sIPTW stabilized inverse probability treatment weighting
  3. *Variable used in the propensity score matching model; de novo vs not de novo were used as categories for initial Dx to metastatic Dx
  4. Race data were not known in the “not documented” race group
  5. Visceral disease was defined as metastatic disease in the lung and/or liver; patients could have had other sites of metastases. No visceral disease was defined as no lung or liver metastases
  6. §Bone-only disease was defined as metastatic disease in the bone only
  7. ǁMultiple metastases at the same site were counted as 1 site (e.g., if a patient had 3 bone metastases in the spine, it was considered only 1 site)