Table 1.
Demographic and clinical characteristics of propensity score-matched study population identified from the SEER database.
| Characteristics | 1:1 PS-matched FPC (N = 31,712), No. (%) |
SPC among breast cancer survivors (N = 31,712), No. (%) |
|---|---|---|
| Age of diagnosis, mean (SD), years | 66.5 (13.2) | 66.6 (13.1) |
| Race | ||
| White | 26279 (82.9%) | 26094 (82.3%) |
| Black | 3442 (10.9%) | 3501 (11.0%) |
| Other | 1991 (6.3%) | 2117 (6.7%) |
| Primary site | ||
| Breast | 13903 (43.8%) | 13931 (43.9%) |
| Lung | 4900 (15.5%) | 4850 (15.3%) |
| Colorectal | 3424 (10.8%) | 3351 (10.6%) |
| Uterus | 2335 (7.4%) | 2392 (7.5%) |
| Lymphoma | 1202 (3.8%) | 1191 (3.8%) |
| Thyroid | 1237 (3.9%) | 1268 (4.0%) |
| Melanoma | 1240 (3.9%) | 1261 (4.0%) |
| Ovary | 1113 (3.5%) | 1095 (3.5%) |
| Pancreas | 1093 (3.4%) | 1130 (3.6%) |
| Leukemia | 1265 (4.0%) | 1243 (3.9%) |
| Tumor stage | ||
| Local | 16760 (52.9%) | 16739 (52.8%) |
| Regional | 7579 (23.9%) | 7591 (23.9%) |
| Distant | 7373 (23.2%) | 7382 (23.3%) |
| Year of diagnosis | ||
| 2000–2004 | 3397 (10.7%) | 3393 (10.7%) |
| 2005–2009 | 10600 (33.4%) | 10592 (33.4%) |
| 2010–2014 | 17715 (55.9%) | 17727 (55.9%) |
| Surgerya | ||
| No/Unknown | 8682 (27.4%) | 8755 (27.6%) |
| Yes | 23030 (72.6%) | 22957 (72.4%) |
| Chemotherapya | ||
| No/Unknown | 21497 (67.8%) | 21476 (67.7%) |
| Yes | 10215 (32.2%) | 10236 (32.3%) |
| Radiotherapya | ||
| No/Unknown | 24792 (78.2%) | 24585 (77.5%) |
| Yes | 6920 (21.8%) | 7127 (22.5%) |
| Characteristics of the prior breast cancer | ||
| Age of diagnosis (year) | ||
| ≤50 | – | 1922 (22.3%) |
| >50 | – | 29790 (77.7%) |
|
Time interval between prior breast cancer and SPC |
||
| 6 months-5 years | – | 17077 (53.9%) |
| >5 years | – | 14635 (46.1%) |
| Tumor stage | ||
| Local | – | 21176 (66.8%) |
| Regional | – | 9441 (29.8%) |
| Distant | – | 658 (2.1%) |
| Unknown | – | 437 (1.4%) |
| Tumor grade | ||
| Grade 1 | – | 6481 (20.4%) |
| Grade 2 | – | 12279 (38.7%) |
| Grade 3&4 | – | 10289 (32.4%) |
| Unknown | – | 2663 (8.4%) |
| Tumor size (mm) | ||
| ≤10 | – | 7843 (24.7%) |
| >10 and ≤20 | – | 11286 (35.6%) |
| >20 and ≤50 | – | 8362 (26.4%) |
| >50 | – | 1694 (5.3%) |
| Unknown | – | 2527 (8.0%) |
| Lymph node status | ||
| Negative | – | 19582 (61.7%) |
| Positive | – | 8785 (27.7%) |
| Unknown | – | 3345 (10.5%) |
| ER status | ||
| Negative | – | 6190 (19.5%) |
| Positive | – | 21920 (69.1%) |
| Unknown | – | 3602 (11.4%) |
| PR status | ||
| Negative | – | 9088 (28.7%) |
| Positive | – | 18563 (58.5%) |
| Unknown | – | 4061 (12.8%) |
| Molecular subtypeb | ||
| ER+ or PR+/HER2− (Luminal A) | – | 2178 (68.4%) |
| ER+ or PR+/HER2+ (Luminal B) | – | 256 (8.0%) |
| ER- and PR−/HER2+ (HER2 Enriched) | – | 120 (3.8%) |
| ER- and PR−/HER2− (Triple Negative) | – | 359 (11.3%) |
| Unknown | – | 271 (8.5%) |
| Surgerya | ||
| No/Unknown | – | 1134 (3.6%) |
| Yes | – | 30578 (96.4%) |
| Chemotherapya | ||
| No/Unknown | – | 19567 (61.7%) |
| Yes | – | 12145 (38.3%) |
| Radiotherapya | ||
| No/Unknown | – | 14617 (46.1%) |
| Yes | – | 17095 (53.9%) |
FPC first primary cancer, SPC second primary cancer, ER estrogen receptor, PR progesterone receptor, HER2 human epidermal growth factor receptor 2, +: positive, −: negative.
aThis indicates initial treatment.
bThis variable is limited to data from 2010 and onwards (N = 3184), because HER2 status is only available after 2010.