Skip to main content

Table 5 Hazard ratios (HRs) of breast cancer-specific mortality among women with primary breast cancer as the second malignancy (BCa-2), stratified clinical characteristics, 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

  BCa-1
N (IR)
BCa-2
N (IR)
HR (95% CI)a
Age at diagnosis, years
 18–44 19,010 (2.0) 164 (2.0) 1.05 (0.90–1.22)
 45–54 25,197 (1.6) 385 (1.7) 1.05 (0.95–1.16)
 55–64 25,246 (1.6) 720 (1.7) 1.19 (1.11–1.28)
 65–74 20,535 (1.7) 978 (1.8) 1.15 (1.08–1.23)
 75–84 16,797 (2.5) 1060 (2.5) 1.10 (1.04–1.17)
  ≥ 85 8179 (6.0) 522 (5.0) 1.01 (0.93–1.11)
P for interaction    0.056
Year of diagnosis
 1990–1993 11,532 (1.8) 344 (2.2) 1.07 (0.96–1.19)
 1994–1997 13,760 (1.8) 393 (1.9) 0.98 (0.89–1.09)
 1998–2001 21,259 (1.7) 516 (1.9) 1.15 (1.05–1.25)
 2002–2005 26,642 (1.8) 740 (2.0) 1.15 (1.06–1.23)
 2006–2009 23,333 (2.0) 890 (2.1) 1.13 (1.06–1.21)
 2010–2015 18,438 (2.4) 946 (2.6) 1.14 (1.07–1.22)
P for interaction    0.136
Histology
 Ductal 79,321 (1.8) 2521 (2.0) 1.13 (1.09–1.18)
 Lobular 9222 (1.9) 393 (2.4) 1.06 (0.95–1.17)
 Mixed 8133 (1.4) 314 (1.8) 1.20 (1.08–1.35)
 Others 18,288 (3.2) 601 (3.5) 1.03 (0.95–1.12)
P for interaction    0.067
Tumor grade
 Well differentiated 5445 (0.5) 294 (0.7) 1.43 (1.27–1.61)
 Moderately differentiated 31,639 (1.4) 1149 (1.6) 1.15 (1.09–1.22)
 Poorly differentiated 53,944 (3.0) 1593 (3.6) 1.18 (1.12–1.24)
 Undifferentiated 2400 (2.9) 52 (3.1) 1.07 (0.82–1.41)
P for interaction    0.011
Tumor size
 0–2 cm 28,594 (0.7) 1264 (1.0) 1.29 (1.22–1.36)
 2–5 cm 45,123 (2.7) 1434 (3.5) 1.15 (1.09–1.21)
  > 5 cm 23,418 (7.4) 563 (8.6) 1.25 (1.15–1.36)
P for interaction    0.011
Tumor stage
 Local 27,833 (0.7) 1293 (1.0) 1.31 (1.24–1.39)
 Regional 48,765 (2.7) 1398 (3.3) 1.07 (1.01–1.13)
 Distant 33,806 (21.2) 981 (26.1) 1.03 (0.97–1.10)
P for interaction    < 0.001
Molecular subtypesb
 HR+/HER2- 8076 (1.5) 447 (1.7) 1.09 (0.99–1.20)
 HR+/HER2+ 1743 (2.3) 75 (2.6) 1.38 (1.09–1.74)
 HR−/HER2+ 1281 (3.9) 62 (5.5) 1.61 (1.25–2.08)
 Triple negative 4322 (5.5) 213 (6.7) 1.18 (1.03–1.36)
P for interaction    0.020
Treatment modesc
 Lumpectomy only 5816 (1.2) 349 (1.7) 1.32 (1.19–1.47)
 Mastectomy only 11,190 (1.3) 510 (1.6) 1.13 (1.03–1.23)
 Chemo−/radio-therapy 12,602 (16.5) 365 (17.9) 1.14 (1.03–1.27)
 Lumpectomy plus chemo/radio-therapy 17,627 (0.8) 555 (0.9) 1.13 (1.03–1.23)
 Mastectomy plus chemo/radio-therapy 28,121 (2.8) 649 (3.3) 1.13 (1.04–1.22)
 Othersd 14,316 (13.9) 664 (14.1) 0.99 (0.92–1.07)
P for interaction    0.002
  1. NOTE. Patients with missing information on tumor stage (N = 14,459, 1.57%), tumor grade (N = 97,126, 10.56%) or size (N = 52,267, 5.68%) or molecular types (N = 24,220, 7.6%) were not included for the corresponding analysis. We added an interaction term between BCa-2 and the risk modifier and reported the statistical significance of the term as P for interaction
  2. Abbreviations: CI Confidence interval, HR+ Hormone-receptor positive, HR- Hormone-receptor negative, HER2 Human epidermal growth factor receptor 2, HR Hazard ratio, IR Mortality rate per 100 person-years, N Number of deaths
  3. 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, radio-therapy, and chemo-therapy
  4. b Information on HER2 status was available from 2010 onward, and thus the analysis was restricted to patients diagnosed thereafter
  5. c Information on surgery was available from 1998 onward, and thus the analysis was restricted to patients diagnosed thereafter
  6. d Others included surgery (no/unknown), chemotherapy (no/unknown), and radiotherapy (no/unknown)