Table 3.
Baseline characteristics of breast cancer patients included from SEER data cohort and between-group comparisons (primary breast cancer vs. second primary breast cancer)
| Characteristics | Unmatched Cohort | 1:2 propensity score matched (PSM) Cohort | ||||
|---|---|---|---|---|---|---|
|
|
|
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| PBC | SPBC | Unadjusted P value | PBC | SPBC | PSM-adjusted P value | |
| N=352861 (%) | N=27994 (%) | N=55984 (%) | (N=27994) | |||
| Age | <0.001 | 0.291 | ||||
| 20-39 | 21732 (6.16) | 572 (2.04) | 1040 (1.86) | 572 | ||
| 40-59 | 160508 (45.49) | 8045 (28.74) | 15923 (28.44) | 8045 | ||
| 60-69 | 82526 (23.39) | 7756 (27.71) | 15573 (27.82) | 7756 | ||
| 70-79 | 55837 (15.82) | 7083 (25.30) | 14368 (25.66) | 7083 | ||
| 80+ | 32258 (9.14) | 4538 (16.21) | 9080 (16.22) | 4538 | ||
| Race | <0.001 | 0.096 | ||||
| White | 282509 (80.06) | 23032 (82.27) | 46383 (82.85) | 23032 | ||
| Black | 30590 (8.67) | 3003 (10.73) | 5860 (10.47) | 3003 | ||
| Other | 39762 (11.27) | 1959 (7.00) | 3741 (6.68) | 1959 | ||
| Marriage status | <0.001 | 0.612 | ||||
| Married | 200791 (56.90) | 14238 (50.86) | 28396 (50.72) | 14238 | ||
| Others | 101765 (28.84) | 10280 (36.72) | 20731 (37.03) | 10280 | ||
| Single | 50305 (14.26) | 3476 (12.42) | 6857 (12.25) | 3476 | ||
| Grade | <0.001 | 0.318 | ||||
| Well | 78435 (22.23) | 6403 (22.87) | 12586 (22.48) | 6403 | ||
| Moderately | 149643 (42.41) | 12302 (43.95) | 24582 (43.91) | 12302 | ||
| Poorly | 124783 (35.36) | 9289 (33.18) | 18816 (33.61) | 9289 | ||
| Laterality | 0.402 | 0.740 | ||||
| Left | 179201 (50.79) | 14144 (50.53) | 28354 (50.65) | 14144 | ||
| Right | 173660 (49.21) | 13850 (49.47) | 27630 (49.35) | 13850 | ||
| Primary site | <0.001 | 0.961 | ||||
| Upper-outer quadrant | 122799 (34.80) | 9047 (32.32) | 18127 (32.38) | 9047 | ||
| Upper-inner quadrant | 41375 (11.73) | 3303 (11.80) | 6628 (11.84) | 3303 | ||
| Lower-inner quadrant | 19768 (5.60) | 1702 (6.08) | 3342 (5.97) | 1702 | ||
| Lower-outer quadrant | 25699 (7.28) | 2092 (7.47) | 4134 (7.39) | 2092 | ||
| Central portion | 17394 (4.93) | 1426 (5.09) | 2807 (5.01) | 1426 | ||
| other site | 125826 (35.66) | 10424 (37.24) | 20946 (37.41) | 10424 | ||
| Histological type | <0.001 | 0.485 | ||||
| IDC | 265209 (75.16) | 20586 (73.54) | 41426 (74.00) | 20586 | ||
| ILC | 26061 (7.38) | 2634 (9.41) | 5156 (9.21) | 2634 | ||
| Mixed | 37538 (10.64) | 1763 (6.30) | 3521 (6.29) | 1763 | ||
| Other | 24053(6.82) | 3011 (10.75) | 5881 (10.50) | 3011 | ||
| Stage | <0.001 | 0.359 | ||||
| I | 166249 (47.11) | 15869 (56.69) | 31747 (56.71) | 15869 | ||
| II | 127280 (36.07) | 8363 (29.87) | 16835 (30.07) | 8363 | ||
| III | 45867 (13.00) | 2542 (9.08) | 5106 (9.12) | 2542 | ||
| IV | 13465 (3.82) | 1220 (4.36) | 2296 (4.10) | 1220 | ||
| Surgery | <0.001 | 0.005 | ||||
| Yes | 336993 (95.50) | 26272 (93.85) | 52811 (94.33) | 26272 | ||
| No | 15868 (4.50) | 1722 (6.15) | 3173 (5.67) | 1722 | ||
| Radiation | <0.001 | 0.239 | ||||
| Yes | 191245 (54.20) | 10628 (37.97) | 21489 (38.38) | 10628 | ||
| No | 161616 (45.80) | 17366 (63.03) | 34495 (61.62) | 17366 | ||
| Chemotherapy | <0.001 | 0.263 | ||||
| Yes | 154833 (43.88) | 8423 (30.09) | 16635 (29.71) | 8423 | ||
| No | 198028 (56.12) | 19571 (69.91) | 39349 (70.29) | 19571 | ||
| Hormone receptor | <0.001 | 0.015 | ||||
| Positive | 288292 (81.70) | 21817 (77.93) | 44039 (78.66) | 21817 | ||
| Negative | 64569 (18.30) | 6177 (22.07) | 11945 (21.34) | 6177 | ||
| Cause of death | <0.001 | <0.001 | ||||
| By breast cancer | 41165 (11.67) | 3337 (11.92) | 6411 (11.45) | 3337 (11.92) | ||
| By other cancer | 2365 (0.67) | 1584 (5.66) | 515 (0.92) | 1584 (5.66) | ||
| Other non-tumor-related cause | 37655 (10.67) | 2569 (9.18) | 9348 (16.7) | 2569 (9.18) | ||
| Alive | 271676 (76.99) | 20504 (73.24) | 39710 (70.93) | 20504 (73.24) | ||
PBC: primary breast cancer; SPBC: second primary breast cancer; IDC: infiltrating ductal carcinoma; ILC: infiltrating lobular carcinoma.