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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)
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BMC Cancer

ISSN: 1471-2407

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