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Table 4 Hazard ratios (HRs) of breast cancer-specific mortality among women with primary breast cancer as the second malignancy (BCa-2), by characteristics of the first malignancy, compared to women with primary breast cancer as the first malignancy (BCa-1): 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

  N (%) of patients N (IR) of deaths HR (95% CI)a
By sites of first malignancy
 Colon and Rectum 6463 (17.8) 681 (2.1) 0.95 (0.88–1.03)
 Uterine corpus 6057 (16.7) 610 (1.8) 0.98 (0.90–1.06)
 Blood 3887 (10.7) 407 (2.3) 1.16 (1.05–1.28)
 Skin 3489 (9.6) 309 (1.6) 0.96 (0.86–1.07)
 Lung and Bronchus 3092 (8.5) 418 (4.1) 1.85 (1.68–2.03)
 Thyroid 2722 (7.5) 207 (1.4) 0.93 (0.81–1.07)
 Ovary 1612 (4.4) 181 (2.3) 1.19 (1.02–1.37)
 Urinary Bladder 1547 (4.3) 177 (2.2) 1.22 (1.05–1.42)
 Kidney 1382 (3.8) 116 (1.9) 1.01 (0.84–1.21)
 Uterine cervix 1123 (3.1) 132 (2.0) 1.01 (0.85–1.20)
 Others 4939 (13.6) 591 (2.9) 1.35 (1.25–1.47)
By tumor stage of first malignancy b
 Localized 20,100 (62.3) 1906 (1.8) 0.98 (0.94–1.03)
 Regional 7088 (22.0) 802 (2.4) 1.20 (1.12–1.29)
 Distant 2661 (8.3) 379 (4.7) 1.63 (1.47–1.80)
 Unstaged 2394 (7.4) 335 (3.3) 1.36 (1.22–1.51)
By chemotherapy and radiotherapy for first malignancy
 No/unknown 24,129 (66.4) 2580 (2.1) 1.09 (1.05–1.13)
 Radiotherapy only 4816 (13.3) 470 (2.3) 1.12 (1.03–1.23)
 Chemotherapy only 4796 (13.2) 505 (2.0) 1.12 (1.02–1.22)
 Chemotherapy plus radiotherapy 2572 (7.1) 274 (2.9) 1.44 (1.28–1.63)
  1. Abbreviations: CI Confidence interval, HR Hazards ratio, IR Mortality rate per 100 person-years, N Number of deaths
  2. a HR was 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, tumor stage, histology, tumor grade, estrogen receptor status, progesterone receptor status, and human epidermal growth factor receptor 2 status, surgery, radiotherapy, and chemotherapy
  3. b BCa-2 patients with blood malignancy as first malignancy were removed from this analysis