Skip to main content

Table 2 Risk ratios of 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 P het.
N (%) N (%)
Tamoxifen use      
 Never 1054 (69) 1425 (64) 1.0 (Referent)   
 Ever 467 (31) 787 (36) 0.76 (0.63–0.92)   
Tamoxifen use according to time since first breast cancer      
 1–4 years      
  Never 423 (72) 644 (65) 1.0 (Referent)   
  Ever 163 (28) 342 (35) 0.67 (0.51–0.88)   
 5–9 years      
  Never 387 (67) 504 (63) 1.0 (Referent)   
  Ever 187 (33) 300 (37) 0.76 (0.57–1.03)   0.3
 ≥10 years      
  Never 244 (68) 277 (66) 1.0 (Referent)   
  Ever 117 (32) 145 (34) 0.95 (0.67–1.34)   
Mean duration of tamoxifen (months) 40.2 40.5   0.8  
Median duration of tamoxifen (months) 44 43   0.6  
 Interquartile range (months) 20–60 18–60    
 Range (months) >0–106 >0–174    
Duration of tamoxifen use      
 Never 1054 (69) 1425 (64) 1.0 (Referent)   
 ≤18 months 92 (6) 165 (7) 0.90 (0.65–1.24)   
 19–53 months 139 (9) 242 (11) 0.76 (0.57–1.00) 0.7e  
 ≥54 months 167 (11) 244 (11) 0.80 (0.61–1.04)   
 Unknownb 69 (5) 136 (6)    
Mean time since last use at reference date for past users (months) 57.1 45.2   0.0001  
Median time since last use at reference date for past users (months) 48 37   0.0001  
 Interquartile range (months) 24–83 13–65    
 Range (months) 1–204 1–186    
Time since last tamoxifen use at reference datec      
 Never 1054 (69) 1425 (64) 1.0 (Referent)   
 Current use, 0 months since last used 131 (9) 249 (11) 0.73 (0.55–0.97)   
 Past use, <37 months since last use 110 (7) 206 (9) 0.73 (0.53–1.00) 0.2e  
 Past use, ≥37 months since last use 161 (11) 208 (9) 0.98 (0.73–1.31)   
 Unknownb 65 (4) 124 (6)    
Time since last tamoxifen use at reference date according to duration of use      
 Never 1054 (69) 1425 (64) 1.0 (Referent)   
 <54 months duration      
  Current used 101 (7) 178 (8) 0.86 (0.62–1.19)   
  Past use, <37 months since last use 53 (3) 112 (5) 0.71 (0.47–1.07)   
  Past use, ≥37 months since last use 77 (5) 117 (5) 0.82 (0.56–1.19)   
 ≥54 months duration     0.01e  
  Current used 28 (2) 69 (3) 0.44 (0.27–0.73)   
  Past use, <37 months since last use 56 (4) 90 (4) 0.71 (0.45–1.12)   
  Past use, ≥37 months since last use 83 (5) 85 (4) 1.25 (0.84–1.86)   
  Unknown durationb 69 (5) 136 (6)    
  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 estrogen receptor/progesterone receptor status (positive for either, negative, unknown) at first diagnosis, radiation (yes, no), chemotherapy (yes, no), and other endocrine therapy (yes, no)
  2. bUnknown not included in model
  3. cCut-point at median for values greater than 0 months in WECARE I and II controls
  4. dCurrent users of tamoxifen at reference date
  5. eOverall P-value
  6. CBC contralateral breast cancer, CI confidence intervals, P-het. P value for heterogeneity, RR risk ratio, UBC unilateral breast cancer