Table 2. Characteristics of the chemotherapy and no chemotherapy groups prior to and after matching via propensity scores.
| PRIOR TO MATCHING | AFTER MATCHING | ||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|
| no chemotherapy | chemotherapy | no chemotherapy | chemotherapy | ||||||||
| N | (%) | N | (%) | p-value | N | (%) | N | (%) | p-value | ||
| All | 23337 | (71.8) | 9165 | (28.2) | . | 4590 | (50) | 4590 | (50) | . | |
| Age (years) | < 35 | 257 | (1.1) | 358 | (3.9) | <0.0001 | 102 | (2.2) | 186 | (4.0) | <0.0001 |
| 35 to 49 | 4630 | (19.8) | 3531 | (38.5) | 1349 | (29.4) | 1346 | (29.3) | |||
| 50 to 65 | 10172 | (43.6) | 4370 | (47.7) | 2274 | (49.5) | 2281 | (49.7) | |||
| > 65 | 8201 | (35.1) | 906 | (9.9) | 865 | (18.8) | 777 | (16.9) | |||
| NA | 77 | (0.3) | 0 | (0) | 0 | (0) | 0 | (0) | |||
| Histological type | Ductal | 15704 | (67.3) | 7594 | (82.9) | <0.0001 | 3593 | (78.3) | 3558 | (77.5) | 0.68 |
| Lobular | 2925 | (12.5) | 926 | (10.1) | 549 | (12.0) | 569 | (12.4) | |||
| Other | 4708 | (20.2) | 645 | (7.0) | 448 | (9.8) | 463 | (10.1) | |||
| Histological tumor size | pT1 | 13989 | (59.9) | 4578 | (49.9) | <0.0001 | 2526 | (55.0) | 2593 | (56.5) | 0.01 |
| pT2 | 4940 | (21.2) | 3761 | (41.0) | 1629 | (35.5) | 1517 | (33.0) | |||
| pT3 | 363 | (1.5) | 351 | (3.8) | 133 | (2.9) | 167 | (3.6) | |||
| pT4 | 45 | (0.2) | 42 | (0.4) | 10 | (0.2) | 22 | (0.5) | |||
| NA | 4000 | (17.1) | 433 | (4.7) | 292 | (6.4) | 291 | (6.4) | |||
| Involved axillary nodes | 0 | 15885 | (68.1) | 2937 | (32.0) | <0.0001 | 2218 | (48.3) | 2207 | (48.1) | <0.0001 |
| 1 to 3 | 3420 | (14.7) | 3978 | (43.4) | 1706 | (37.2) | 1526 | (33.2) | |||
| 4 to 9 | 826 | (3.5) | 1519 | (16.6) | 473 | (10.3) | 611 | (13.3) | |||
| ≥ 10 | 297 | (1.3) | 600 | (6.6) | 193 | (4.2) | 246 | (5.3) | |||
| NA | 2909 | (12.5) | 131 | (1.4) | 0 | (0) | 0 | (0) | |||
| SBR grade | 1 | 7553 | (32.4) | 1279 | (14.0) | <0.0001 | 929 | (20.2) | 1001 | (21.8) | 0.003 |
| 2 | 9000 | (38.6) | 3703 | (40.4) | 1934 | (42.1) | 2031 | (44.2) | |||
| 3 | 4903 | (21.0) | 4014 | (43.8) | 1727 | (37.7) | 1558 | (34.0) | |||
| NA | 1881 | (8.0) | 169 | (1.8) | 0 | (0) | 0 | (0) | |||
| Hormone receptor status | Hormone receptor + | 17424 | (74.7) | 6492 | (70.8) | <0.0001 | 3349 | (75.1) | 3446 | (75.1) | 0.82 |
| Hormone receptor - | 2349 | (10.0) | 2155 | (23.5) | 763 | (16.7) | 779 | (17.0) | |||
| NA | 3564 | (15.3) | 518 | (5.7) | 378 | (8.2) | 365 | (7.9) | |||
| Years of diagnosis | 1981–1983 | 2080 | (89.1) | 251 | (2.7) | <0.0001 | 160 | (3.5) | 171 | (3.7) | <0.0001 |
| 1984–1988 | 3630 | (15.6) | 771 | (8.4) | 516 | (11.2) | 493 | (10.7) | |||
| 1989–1993 | 4452 | (19.1) | 1434 | (15.6) | 978 | (21.3) | 950 | (20.7) | |||
| 1994–1998 | 4616 | (19.8) | 1791 | (19.5) | 956 | (20.8) | 1060 | (23.1) | |||
| 1999–2003 | 3164 | (13.6) | 1748 | (19.1) | 705 | (15.3) | 818 | (17.8) | |||
| 2003–2008 | 5395 | (23.1) | 3170 | (34.6) | 1275 | (27.8) | 1098 | (23.9) | |||
| Propensity score | Mean (sd) | 0.28 (0.20) | 0.69 (0.20) | <0.0001 | 0.42 (0.25) | 0.43 (0.25) | 0.22 | ||||
NA: not assessable. pT1: pathological tumor size ≤ 2 cm. pT2: tumor > 2 cm and ≤ 5 cm. pT3: > 5 cm. pT4 = extension to skin and/or chest wall. SBR: Scarff Bloom and Richardson. sd: standard deviation.