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Table 2 Associations of tumor characteristics and treatment modes with primary breast cancer as the second malignancy (BCa-2): a SEER population-based study in US, 1990–2015

From: Increased risk of breast cancer-specific mortality among cancer survivors who developed breast cancer as a second malignancy

  BCa-1 BCa-2
N (%) N (%) OR (95% CI) a
Histology
 Ductal 643,139 (72.8) 25,487 (70.2) 1.00
 Lobular 73,112 (8.3) 3456 (9.5) 1.01 (0.97–1.05)
 Mixed 82,546 (9.3) 3439 (9.5) 1.02 (0.98–1.06)
 Others 85,084 (9.6) 3931 (10.8) 1.04 (1.00–1.08)
Tumor grade
 Well differentiated 165,869 (18.8) 7817 (21.5) 1.00
 Moderately differentiated 337,563 (38.2) 14,526 (40.0) 0.97 (0.94–1.00)
 Poorly differentiated 277,729 (31.4) 9435 (26.0) 0.91 (0.88–0.94)
 Undifferentiated 9863 (1.1) 266 (0.7) 0.86 (0.76–0.98)
Tumor size
 0-2 cm 506,784 (57.3) 22,629 (62.3) 1.00
 2-5 cm 260,786 (29.5) 9608 (26.5) 0.85 (0.83–0.87)
  > 5 cm 66,236 (7.5) 1884 (5.2) 0.67 (0.64–0.71)
Tumor stage
 Local 547,036 (61.9) 24,624 (67.8) 1.00
 Regional 265,617 (30.1) 8815 (24.3) 0.86 (0.84–0.88)
 Distant 57,578 (6.5) 2065 (5.7) 0.79 (0.75–0.83)
Molecular subtypesc
 HR+/HER2- 205,424 (67.4) 11,106 (70.4) 1.00
 HR+/HER2+ 30,893 (10.1) 1283 (8.1) 0.93 (0.88–0.99)
 HR−/HER2+ 13,507 (4.4) 492 (3.1) 0.82 (0.75–0.90)
 Triple negative 32,172 (10.6) 1481 (9.4) 1.00 (0.94–1.05)
  N (%) N (%) OR (95% CI) b
Surgery d
 No 60,648 (7.8) 3712 (11.6) 1.00
 Lumpectomy 404,612 (52.3) 17,372 (54.1) 0.75 (0.72–0.79)
 Mastectomy 304,812 (39.4) 10,900 (33.9) 0.74 (0.71–0.78)
Chemotherapy
 No/unknown 536,470 (60.7) 27,537 (75.8) 1.00
 Yes 347,411 (39.3) 8776 (24.2) 0.84 (0.81–0.86)
Radiotherapy
 No/unknown 462,215 (52.3) 21,631 (59.6) 1.00
 Yes 421,666 (47.7) 14,682 (40.4) 0.83 (0.82–0.85)
Treatment modesd
 Lumpectomy only 79,295 (10.3) 5149 (16.0) 1.00
 Mastectomy only 138,766 (17.9) 6648 (20.7) 0.88 (0.85–0.92)
 Chemo−/radio-therapy 27,038 (3.5) 1038 (3.2) 1.05 (0.97–1.13)
 Lumpectomy plus chemo−/radio-therapy 325,317 (42.1) 12,223 (38.0) 0.79 (0.76–0.82)
 Mastectomy plus chemo−/radio-therapy 166,046 (21.5) 4252 (13.2) 0.74 (0.71–0.78)
 Otherse 36,829 (4.8) 2817 (8.8) 1.16 (1.10–1.23)
  1. NOTE. Patients with missing information on tumor stage (N = 14,459, 1.57%), tumor grade (N = 97,126, 10.56%), tumor size (N = 52,267, 5.68%), molecular types (N = 24,220, 7.6%) or surgery (N = 3362, 0.4%) were not included in the corresponding analysis
  2. Abbreviations: BCa-1 Breast cancer as the first malignancy, CI Confidence interval, HR Hormone-receptor, HER2 Human epidermal growth factor receptor 2, N Number; OR Odds ratio
  3. a The models were adjusted for age (continuous) and calendar period at diagnosis, race, cohabitation status, percentile of cost of living and high-school education in county of residence
  4. b The models were additionally adjusted for tumor stage, histology, tumor grade, ER status, PR status, and HER2 status
  5. c Information on HER2 status was available from 2010 onward, and thus the analysis was restricted to patients diagnosed thereafter
  6. d Information on surgery and therapy was available from 1998 onward, and thus the analysis was restricted to patients diagnosed thereafter
  7. e Others included surgery (no/unknown), chemotherapy (no/unknown), and radiotherapy (no/unknown)