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Table 5 Risk ratios of contralateral breast cancer associated with chemotherapy by time, patient, and tumor characteristics

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

 

No chemotherapy

Chemotherapy

 

CBC cases

UBC controls

RR

CBC cases

UBC controls

RRa (95 % CI)

P het.

N (%)

N (%)

 

N (%)

N (%)

Ever use of chemotherapy (yes/no)

699 (46)

923 (42)

1.0

822 (54)

1,289 (58)

0.71 (0.59–0.85)

 

Time since first breast cancer (years)

       

 1–4

278 (47)

402 (41)

1.0

308 (53)

584 (59)

0.59 (0.45–0.77)

 

 5–9

249 (43)

322 (40)

1.0

325 (57)

482 (60)

0.73 (0.56–0.95)

0.1

 ≥10

172 (48)

199 (47)

1.0

189 (52)

223 (53)

0.92 (0.65–1.30)

 

Age at 1st breast cancer (years)b

       

 ≤39

59 (22)

88 (23)

1.0

209 (78)

296 (77)

0.99 (0.63–1.57)

 

 40–49

372 (46)

469 (40)

1.0

436 (54)

711 (60)

0.65 (0.52–0.82)

0.2

 50–54

268 (60)

366 (56)

1.0

177 (40)

282 (44)

0.70 (0.52–0.94)

 

Year of diagnosis of first breast cancer

       

 1985–1989

192 (63)

295 (51)

1.0

111 (37)

285 (49)

0.66 (0.46–0.95)

 

 1990–1994

283 (49)

392 (45)

1.0

289 (51)

479 (55)

0.71 (0.55–0.92)

 

 1995–1999

157 (37)

190 (34)

1.0

269 (63)

361 (66)

0.79 (0.58–1.08)

0.5

 2000–2004

58 (31)

40 (21)

1.0

128 (69)

150 (79)

0.47 (0.27–0.83)

 

 2005–2008

9 (26)

6 (30)

1.0

25 (74)

14 (70)

1.17 (0.31–4.43)

 

First-degree family history of breast cancerc

       

 Yes

219 (44)

211 (45)

1.0

279 (56)

259 (55)

0.89 (0.65–1.20)

 

 No

474 (47)

704 (41)

1.0

536 (53)

1,013 (59)

0.65 (0.53–0.80)

0.07

 Unknownd

6 (46)

8 (32)

1.0

7 (54)

17 (68)

  

BMI at first breast cancer (kg/m2)

       

 <25

538 (51)

660 (44)

1.0

514 (49)

837 (56)

0.66 (0.53-0.81)

 

 25–29.9

107 (36)

192 (39)

1.0

192 (64)

304 (61)

0.83 (0.59-1.18)

0.3

 ≥30

52 (31)

68 (32)

1.0

114 (69)

147 (68)

0.89 (0.55-1.44)

 

 Unknownd

2 (50)

3 (75)

1.0

2 (50)

1 (25)

  

Histology of first breast cancere

       

 Lobular

86 (48)

94 (42)

1.0

93 (52)

129 (58)

0.77 (0.49–1.21)

 

 Other

610 (46)

828 (42)

1.0

728 (54)

1,158 (58)

0.70 (0.58–0.85)

0.7

 Unknownd

3 (75)

1 (33)

 

1 (25)

2 (67)

  

ER/PR status of first breast cancerf

       

 Positive

419 (49)

609 (44)

1.0

444 (51)

770 (56)

0.72 (0.57–0.91)

 

 Negative

91 (22)

96 (20)

1.0

322 (78)

377 (80)

0.67 (0.45–1.02)

0.8

 Unknownd

189 (77)

218 (61)

1.0

56 (23)

142 (39)

  
  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 breast cancer diagnosis, radiation therapy (yes, no), and 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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