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Table 4 Risk ratios of contralateral breast cancer associated with tamoxifen use by patient and tumor characteristics

From: Systemic therapy for breast cancer and risk of subsequent contralateral breast cancer in the WECARE Study

 

No tamoxifen

Tamoxifen

 

CBC cases

UBC controls

RR

CBC cases

UBC controls

RRa (95 % CI)

P het.

N (%)

N (%)

 

N (%)

N (%)

Age at 1st breast cancer (years)b

       

 ≤39

222 (83)

293 (76)

1.0

46 (17)

91 (24)

0.69 (0.43–1.10)

 

 40–49

559 (69)

782 (66)

1.0

249 (31)

398 (34)

0.79 (0.62–1.01)

0.9

 50–54

273 (61)

350 (54)

1.0

172 (39)

298 (46)

0.75 (0.56–1.00)

 

Year of diagnosis of first breast cancer

       

 1985–1989

250 (83)

472 (81)

1.0

53 (17)

108 (19)

1.18 (0.75–1.87)

 

 1990–1994

400 (70)

564 (65)

1.0

172 (30)

307 (35)

0.86 (0.65–1.13)

 

 1995–1999

280 (66)

306 (56)

1.0

146 (34)

245 (44)

0.65 (0.48–0.88)

0.1

 2000–2004

101 (54)

71 (37)

1.0

85 (46)

119 (63)

0.52 (0.32–0.85)

 

 2005–2008

23 (68)

12 (60)

1.0

11 (32)

8 (40)

0.88 (0.26–2.92)

 

First-degree family history of breast cancerc

       

 Yes

344 (69)

298 (63)

1.0

154 (31)

172 (37)

0.82 (0.60–1-12)

 

 No

703 (70)

1115 (65)

1.0

307 (30)

602 (35)

0.76 (0.62–0.94)

0.7

 Unknownd

7 (54)

12 (48)

1.0

6 (46)

13 (52)

  

BMI at 1st breast cancer (kg/m2)

       

 <25

749 (71)

991 (66)

1.0

303 (29)

506 (34)

0.76 (0.61–0.95)

 

 25–29.9

191 (64)

307 (62)

1.0

108 (36)

189 (38)

0.81 (0.57–1.15)

0.9

 ≥30

111 (67)

124 (58)

1.0

55 (33)

91 (42)

0.71 (0.44–1.14)

 

 Unknownd

3 (75)

3 (75)

1.0

1 (25)

1 (25)

  

Histology of first breast cancere

       

 Lobular

112 (63)

103 (46)

1.0

67 (37)

120 (54)

0.48 (0.31–0.75)

0.03

 Other

940 (70)

1,321 (67)

1.0

398 (30)

665 (33)

0.82 (0.67–0.99)

 

 Unknownd

2 (50)

1 (33)

 

2 (50)

2 (67)

  

ER/PR status of first breast cancerf

       

 Positive

450 (52)

679 (49)

1.0

413 (48)

700 (51)

0.75 (0.60–0.93)

 

 Negative

388 (94)

422 (89)

1.0

25 (6)

51 (11)

0.54 (0.30–0.98)

0.3

 Unknownd

216 (88)

324 (90)

1.0

29 (12)

36 (10)

  
  1. aAdjusted for age at first breast cancer diagnosis (continuous), first-degree family history of breast cancer (yes, no, unknown), histology (lobular, other, unknown), stage (local, regional, unknown) and ER/PR status (positive for either, negative, unknown) at first diagnosis, radiation (yes, no), chemotherapy (yes, no), and other endocrine therapy (yes, no)
  2. bRR are adjusted for all variables listed in footnote “a”, except age at first breast cancer diagnosis
  3. cRR are adjusted for all variables listed in footnote “a”, except first-degree family history of breast cancer
  4. dUnknown not included in model
  5. eRR are adjusted for all variables listed in footnote “a”, except histology of first breast cancer diagnosis
  6. fRR are adjusted for all variables listed in footnote “a”, except ER/PR status of first breast cancer diagnosis
  7. BMI body mass index, CBC contralateral breast cancer, CI confidence interval, ER/PR estrogen receptor/progesterone receptor, P het; P value for heterogeneity, RR risk ratio, UBC unilateral breast cancer
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Breast Cancer Research

ISSN: 1465-542X

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