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Table 3 Risk of breast cancer subgroups defined by immunohistochemical markers in relation to total duration of breastfeeding

From: Breastfeeding in relation to risk of different breast cancer characteristics

Tumour subgroup Breastfeeding total in months Number of cases Incidence/100000 RR RR*
Ki67 low      
(≤10%)# <4.0 54 182 1.00 1.00
  ≥4.0 - <8.0 76 203 1.11 (0.78 - 1.57) 1.06 (0.74 - 1.51)
  ≥8.0 - <13.0 72 201 1.09 (0.77 - 1.56) 1.01 (0.69 - 1.47)
  ≥13.0 58 165 0.90 (0.62 - 1.31) 0.82 (0.53 - 1.25)
  Missing 11 183 --- ---
  Total 271 188 p-trend:0.54 p-trend:0.44
Ki67 high      
(>10%) <4.0 17 57 1.00 1.00
  ≥4.0 - <8.0 21 56 0.98 (0.51 - 1.85) 1.02 (0.53 - 1.96)
  ≥8.0 - <13.0 26 72 1.25 (0.68 - 2.31) 1.39 (0.72 - 2.67)
  ≥13.0 30 85 1.48 (0.82 - 2.69) 1.88 (0.94 - 3.76)
  Missing 7 116 --- ---
  Total 101 70 p-trend:0.11 p-trend:0.03
HER2 (0-1+)#      
  <4.0 57 192 1.00 1.00
  ≥4.0 - <8.0 78 208 1.08 (0.77 - 1.52) 1.02 (0.72 - 1.45)
  ≥8.0 - <13.0 84 234 1.21 (0.86 - 1.69) 1.12 (0.78 - 1.61)
  ≥13.0 73 207 1.07 (0.76 - 1.52) 1.07 (0.72 - 1.59)
  Missing 19 499 --- ---
  Total 311 216 p-trend:0.58 p-trend:0.44
HER2 (2 + -3+)      
  <4.0 9 30 1.00 1.00
  ≥4.0 - <8.0 9 24 0.80 (0.32 - 2.01) 1.02 (0.39 - 2.65)
  ≥8.0 - <13.0 11 31 1.02 (0.42 - 2.46) 1.40 (0.53 - 3.69)
  ≥13.0 11 31 1.03 (0.43 - 2.49) 1.35 (0.46 - 3.97)
  Missing 1 17 --- ---
  Total 41 28 p-trend:0.79 p-trend:0.59
Cyclin D1 low      
(≤10%) # <4.0 54 182 1.00 1.00
  ≥4.0 - <8.0 82 219 1.20 (0.85 - 1.69) 1.15 (0.81 - 1.64)
  ≥8.0 - <13.0 73 203 1.11 (0.78 - 1.58) 1.05 (0.72 - 1.53)
  ≥13.0 73 122 1.14 (0.80 - 1.62) 1.06 (0.71 - 1.60)
  Missing 13 216 --- ---
  Total 295 205 p-trend:0.65 p-trend:0.77
Cyclin D1 high      
(>10%) <4.0 14 47 1.00 1.00
  ≥4.0 - <8.0 14 37 0.79 (0.37 - 1.65) 0.84 (0.39 - 1.78)
  ≥8.0 - <13.0 24 67 1.38 (0.72 - 2.68) 1.56 (0.77 - 3.19)
  ≥13.0 20 57 1.19 (0.60 - 2.36) 1.61 (0.73 - 3.56)
  Missing 6 100 --- ---
  Total 78 54 p-trend:0.29 p-trend:0.10
P27 low      
(≤10%) # <4.0 21 71 1.00 1.00
  ≥4.0 - <8.0 41 109 1.55 (0.91 - 2.62) 1.56 (0.91 - 2.67)
  ≥8.0 - <13.0 31 86 1.22 (0.70 - 2.12) 1.21 (0.68 - 2.18)
  ≥13.0 35 99 1.40 (0.82 - 2.41) 1.35 (0.73 - 2.50)
  Missing 7 116 --- ---
  Total 135 94 p-trend:0.47 p-trend:0.61
P27 high      
(>10%) <4.0 48 162 1.00 1.00
  ≥4.0 - <8.0 53 141 0.87 (0.59 - 1.29) 0.83 (0.55 - 1.24)
  ≥8.0 - <13.0 65 181 1.11 (0.76 - 1.61) 1.04 (0.70 - 1.56)
  ≥13.0 53 151 0.93 (0.63 - 1.37) 0.93 (0.59 - 1.46)
  Missing 11 183 --- ---
  Total 230 159 p-trend:0.95 p-trend:0.73
  1. *Adjusted for age at baseline (continuous), education, socioeconomic status, marital status, age at menarche, age at first birth, parity, oophorectomy, age at menopause, oral contraceptive use, hormone replacement therapy use, bmi, alcohol consumption, smoking and height.
  2. #Reference group in heterogeneity analyses.