Skip to main content

Table 3 Risk ratios of ER-positive and ER-negative contralateral breast cancer associated with different aspects of tamoxifen use

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

Use of tamoxifen CBC cases UBC controls RRa (95 % CI) P value
N (%) N (%)
ER-positive CBCb     
  Never 525 (63) 692 (62) 1.0 (referent)  
  Ever 303 (37) 421 (38) 0.75 (0.58–0.96)  
 Duration of tamoxifen use     
  Never 525 (63) 692 (62) 1.0 (referent)  
  <54 months 142 (17) 198 (18) 0.84 (0.61–1.15)  
  ≥54 months 117 (14) 149 (13) 0.80 (0.57–1.12)  
  Unknownc 44 (5) 74 (7)   
  Test for trend     0.2
  Overall P value     0.3
 Time since last use at reference date     
  Never 525 (63) 692 (62) 1.0 (referent)  
  Current use, duration <54 months 56 (7) 83 (7) 0.82 (0.52–1.30)  
  Current use, duration ≥54 months 20 (2) 41 (4) 0.38 (0.20–0.72)  
  Past use, <37 months since last use 68 (8) 97 (9) 0.72 (0.47–1.12)  
  Past use, ≥37 months since last use 116 (14) 131 (12) 1.07 (0.74–1.56)  
  Unknownc 43 (5) 69 (6)   
  Overall P value     0.02
ER-negative CBCb     
  Never 282 (78) 318 (64) 1.0 (referent)  
  Ever 79 (22) 180 (36) 0.92 (0.59–1.44)  
 Duration of tamoxifen use     
  Never 282 (78) 318 (64) 1.0 (referent)  
  <54 months 39 (11) 87 (17) 1.03 (0.58–1.82)  
  ≥54 months 29 (8) 58 (12) 0.93 (0.50–1.74)  
  Unknownc 11 (3) 35 (7)   
  Test for trend     0.9
  Overall P value     1.0
 Time since last use at reference date     
  Never 282 (78) 318 (64) 1.0 (referent)  
  Current use, duration <54 months 18 (5) 35 (7) 1.54 (0.68–3.47)  
  Current use, duration ≥54 months 5 (1) 14 (3) 0.76 (0.25–2.37)  
  Past use, <37 months since last use 21 (6) 45 (9) 1.12 (0.55–2.27)  
  Past use, ≥37 months since last use 25 (7) 55 (11) 0.66 (0.31–1.42)  
  Unknownc 10 (3) 31 (6)   
  Overall P value     0.6
  1. CBC contralateral breast cancer, CI confidence intervals, ER estrogen receptor, RR risk ratio, UBC unilateral breast cancer
  2. 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/progesterone receptor status (positive for either, negative, unknown) at first diagnosis, radiation (yes, no), chemotherapy (yes, no), and other endocrine therapy (yes, no)
  3. bThese models are subset models (two separate models for ER-positive CBC and ER-negative CBC). ER status for CBC was missing for 332 cases
  4. cUnknown not included in model