TABLE 1.
Patient Characteristics Before and After Overlap Propensity Score Weighting
| Characteristic | Before Propensity Score Weighting | After Propensity Score Weighting | ||||
|---|---|---|---|---|---|---|
| Axillary Staging (n = 121,708) | No Axillary Staging (n = 22,621) | SMD | Axillary Staging (n = 16,524)* | No Axillary Staging (n = 16,524)* | SMD | |
| Age, mean (SD) | 76.98 (5.34) | 81.64 (6.72) | 0.768 | 80.25 (5.88) | 80.25 (6.38) | <0.001 |
| Year at diagnosis, n (%) | ||||||
| 2005 | 9907 (8.1) | 2129 (9.4) | 0.078 | 1517.9 (9.2) | 1517.9 (9.2) | <0.001 |
| 2006 | 10,242 (8.4) | 2011 (8.9) | 1465.8 (8.9) | 1465.8 (8.9) | ||
| 2007 | 10,660 (8.8) | 1821 (8.1) | 1352.2 (8.2) | 1352.2 (8.2) | ||
| 2008 | 10,811 (8.9) | 1903 (8.4) | 1401.1 (8.5) | 1401.1 (8.5) | ||
| 2009 | 11,243 (9.2) | 1850 (8.2) | 1384.2 (8.4) | 1384.2 (8.4) | ||
| 2010 | 10,955 (9.0) | 1827 (8.1) | 1359.7 (8.2) | 1359.7 (8.2) | ||
| 2011 | 11,263 (9.3) | 2073 (9.2) | 1514.3 (9.2) | 1514.3 (9.2) | ||
| 2012 | 11,392 (9.4) | 2177 (9.6) | 1578.5 (9.6) | 1578.5 (9.6) | ||
| 2013 | 11,709 (9.6) | 2193 (9.7) | 1596.1 (9.7) | 1596.1 (9.7) | ||
| 2014 | 11,629 (9.6) | 2351 (10.4) | 1685.3 (10.2) | 1685.3 (10.2) | ||
| 2015 | 11,897 (9.8) | 2286 (10.1) | 1668.9 (10.1) | 1668.9 (10.1) | ||
| Marital status, n (%) | ||||||
| Married | 55,267 (45.4) | 7689 (34.0) | 0.235 | 6142.6 (37.2) | 6142.6 (37.2) | <0.001 |
| Nonmarried | 66,441 (54.6) | 14,932 (66.0) | 10,381.4 (62.8) | 10,381.4 (62.8) | ||
| Race, n (%) | ||||||
| Black | 9311 (7.7) | 1622 (7.2) | 0.057 | 1204.9 (7.3) | 1204.9 (7.3) | <0.001 |
| Other | 7565 (6.2) | 1132 (5.0) | 869.7 (5.3) | 869.7 (5.3) | ||
| White | 10,4832 (86.1) | 19,867 (87.8) | 14,449.5 (87.4) | 14,449.5 (87.4) | ||
| Histology, n (%) | ||||||
| Cystic, mucinous, and serous neoplasms | 4340 (3.6) | 1172 (5.2) | 0.111 | 780.8 (4.7) | 780.8 (4.7) | <0.001 |
| Ductal and lobular neoplasms | 114,639 (94.2) | 20,659 (91.3) | 15,220.0 (92.1) | 15,220.0 (92.1) | ||
| Other | 2729 (2.2) | 790 (3.5) | 523.3 (3.2) | 523.3 (3.2) | ||
| Surgery type, n (%) | ||||||
| Lumpectomy | 73,871 (60.7) | 17,250 (76.3) | 0.34 | 11,976.4 (72.5) | 11,976.4 (72.5) | <0.001 |
| Mastectomy | 47,837 (39.3) | 5371 (23.7) | 4547.7 (27.5) | 4547.7 (27.5) | ||
| Tumor grade, n (%) | ||||||
| I | 34,558 (28.4) | 7377 (32.6) | 0.111 | 5254.7 (31.8) | 5254.7 (31.8) | <0.001 |
| II | 57,772 (47.5) | 10,607 (46.9) | 7801.2 (47.2) | 7801.2 (47.2) | ||
| III | 28,819 (23.7) | 4522 (20.0) | 3384.5 (20.5) | 3384.5 (20.5) | ||
| IV | 559 (0.5) | 115 (0.5) | 83.7 (0.5) | 83.7 (0.5) | ||
| ER positive, n (%) | 105,889 (87.0) | 20,158 (89.1) | 0.065 | 14,663.8 (88.7) | 14,663.8 (88.7) | <0.001 |
| PR positive, n (%) | 91,453 (75.1) | 17,473 (77.2) | 0.049 | 12,714.3 (76.9) | 12,714.3 (76.9) | <0.001 |
| Tumor size, n (%) | ||||||
| <2 cm | 81,356 (66.8) | 15,884 (70.2) | 0.073 | 11,650.5 (70.5) | 11,650.5 (70.5) | <0.001 |
| ≥2 cm | 40,352 (33.2) | 6737 (29.8) | 4873.5 (29.5) | 4873.5 (29.5) | ||
| History of previous cancer, n (%) | 94,550 (77.7) | 14,276 (63.1) | 0.323 | 10,879.1 (65.8) | 10,879.1 (65.8) | <0.001 |
| Number of previous tumors, n (%) | ||||||
| 1 | 77,447 (63.6) | 11,698 (51.7) | 0.266 | 8891.2 (53.8) | 8891.2 (53.8) | <0.001 |
| 2 | 33,741 (27.7) | 7517 (33.2) | 5361.8 (32.4) | 5361.8 (32.4) | ||
| 3+ | 10,520 (8.6) | 3406 (15.1) | 2271.0 (13.7) | 2271.0 (13.7) | ||
| Radiotherapy†, n (%) | ||||||
| Yes | 55,891 (45.9) | 5345 (23.6) | 0.481 | 7831.1 (47.4) | 4159.9 (25.2) | 0.475 |
| No/unknown | 65,817 (54.1) | 17,276 (76.4) | 8692.9 (52.6) | 12,364.1 (74.8) | ||
| Chemotherapy†, n (%) | ||||||
| Yes | 16,690 (13.7) | 874 (3.9) | 0.353 | 1380.1 (8.4) | 763.6 (4.6) | 0.152 |
| No/unknown | 105,018 (86.3) | 21,747 (96.1) | 15,144.0 (91.6) | 15,760.4 (95.4) | ||
Balance between the groups is assessed using SMDs. Larger values indicate a greater difference, with values >0.1 defined as an important difference and bolded.
*Sample sizes represent the weighted size of the cohort.
†Radiotherapy and chemotherapy were not included in the propensity score model.
PR indicates progesterone receptor; SMD, standardized mean difference.