Skip to main content

Table 3. Associations between breast cancer risk factors and ER status in Kenyan breast cancer patients (N=838)

From: Breast cancer risk factors in relation to molecular subtypes in breast cancer patients from Kenya

  ER+ N=582 ER- N=256 ER- vs. ER+
N % N % OR (95% CI)† P†
Age at diagnosis/year
 20–39 155 26.8 54 21.1 1.00 (Ref)  
 40–49 166 28.7 76 29.7 1.38 (0.82, 2.32) 0.23
 50–59 138 23.9 73 28.5 1.20 (0.51, 2.83) 0.68
 ≥ 60 119 20.6 53 20.7 0.84 (0.30, 2.35) 0.74
 Trend‡      0.995 (0.72, 1.39) 0.98
BMI/ kg/m2
 Normal (< 25.0) 136 29.8 74 34.6 1.00 (Ref)  
 Overweight (25.0–29.9) 185 40.5 79 36.9 0.77 (0.49, 1.21) 0.26
 Obese (≥ 30.0) 136 29.8 61 28.5 0.84 (0.51, 1.38) 0.49
 Trend‡      0.92 (0.71, 1.18) 0.49
Premenopausal: BMIa
 Normal (< 25.0) 89 34.6 41 39.8 1.00 (Ref)  
 Overweight (25.0–29.9) 102 39.7 30 29.1 0.58 (0.31, 1.10) 0.09
 Obese (≥ 30.0) 66 25.7 32 31.1 0.91 (0.46, 1.77) 0.77
 Trend‡      0.93 (0.66, 1.31) 0.69
Postmenopausal: BMIa
 Normal (< 25.0) 47 23.6 33 29.7 1.00 (Ref)  
 Overweight (25.0–29.9) 83 41.7 49 44.1 1.07 (0.55, 2.08) 0.85
 Obese (≥ 30.0) 69 34.7 29 26.1 0.77 (0.37, 1.61) 0.49
 Trend‡      0.87 (0.61, 1.26) 0.47
Age at menarche/year
 ≤ 13 (9–13) 141 25.4 57 23.2 1.00 (Ref)  
 14 139 25.0 71 28.9 1.57 (0.94, 2.61) 0.083
 ≥ 15 (15–20) 276 49.6 118 48.0 1.29 (0.81, 2.04) 0.28
 Trend‡      1.10 (0.88, 1.37) 0.41
Age at first pregnancy/year
 < 20 130 22.9 86 34.1 1.00 (Ref)  
 20–24 253 44.5 108 42.9 0.71 (0.44, 1.15) 0.16
 25–29 115 20.2 35 13.9 0.58 (0.30, 1.11) 0.10
 Nulliparousb or age ≥30 70 12.3 23 9.1 1.14 (0.48, 2.70) 0.76
 Trend‡      0.92 (0.71, 1.20) 0.54
Parity       
 Nulliparousb 37 6.4 7 2.7 0.36 (0.10, 1.32) 0.12
 Parous 545 93.6 249 97.3 1.00 (Ref)  
Number of children
 1–2 171 31.4 55 22.1 1.00 (Ref)  
 3–4 217 39.8 90 36.1 1.43 (0.86, 2.36) 0.16
 ≥ 5 157 28.8 104 41.8 2.03 (1.11, 3.72) 0.021
 Trend‡      1.43 (1.05, 1.93) 0.021
Cumulative breastfeeding duration/monthc
 Q1: 1–< 39 152 28.8 39 16.2 1.00 (Ref)  
 Q2: 39–< 62 127 24.1 65 27.0 2.38 (1.33, 4.24) 0.0033
 Q3: 62–< 96 124 23.5 58 24.1 1.44 (0.74, 2.80) 0.28
 Q4: ≥ 96 124 23.5 79 32.8 1.58 (0.76, 3.30) 0.22
 Trend‡      1.10 (0.87, 1.39) 0.43
Mean breastfeeding duration per child/month
 < 12 84 15.9 36 14.9 1.00 (Ref)  
  12–23 277 52.6 130 53.9 1.10 (0.62, 1.94) 0.74
 ≥ 24 166 31.5 75 31.1 1.25 (0.68, 2.30) 0.48
 Trend‡      1.12 (0.83, 1.51) 0.45
Age at first pregnancy and number of children
 Age 25+ years, 1–3 births 117 22.0 37 15.0 1.00 (Ref)  
 Age < 25 years, 1–3 births 173 32.6 71 28.9 1.20 (0.68, 2.12) 0.53
 Age 25+ years, 4+ births 34 6.4 15 6.1 1.47 (0.60, 3.61) 0.40
 Age < 25 years, 4+ births 207 39.0 123 50.0 1.69 (0.93, 3.05) 0.085
 Trend‡      1.19 (0.99, 1.43) 0.063
Number of children and cumulative breastfeeding duration
 Nulliparous or ≤ 3 children and < 62 months 265 47.0 89 35.9 1.00 (Ref)  
 ≤ 3 children and ≥ 62 months 56 9.9 23 9.3 1.09 (0.56, 2.09) 0.81
 ≥ 4 children and < 62 months 51 9.0 22 8.9 1.52 (0.74, 3.09) 0.25
 ≥ 4 children and ≥ 62 months 192 34.0 114 46.0 1.44 (0.89, 2.34) 0.14
 Trend‡      1.14 (0.97, 1.33) 0.12
Menopausal statusa
 Premenopausal 317 54.6 121 47.5 1.00 (Ref)  
 Postmenopausal 264 45.4 134 52.5 1.44 (0.74, 2.81) 0.28
Age at menopause/yeard
 < 50 117 21.8 74 31.5 1.00 (Ref)  
> 50 102 19.0 40 17.0 0.73 (0.40, 1.36) 0.32
  1. † Point estimates and 95% confidence intervals were from multivariable models, adjusting for the same series of covariates (except where noticed): age at diagnosis, BMI, age at menarche, age at first pregnancy, number of children, mean breastfeeding duration per child, age at menopause, family history of breast cancer in first-degree female relative, occupation, education level, and location of facility. Estimates of numbers of children, cumulative and averaged breastfeeding duration, and combined age at first pregnancy and number of children were computed among parous women. ‡ Results were from the trend analysis using the categorical risk factor as a trend. aMultivariable modeling analysis without adjusting for age at menopause. bWomen who reported never pregnant, never gave birth, and had no child were grouped as “Nulliparous” in modeling analyses. c Multivariable modeling analysis without adjusting for mean breastfeeding duration per child. d Multivariable Modeling analysis was restricted to postmenopausal women. BMI, body mass index; CI, confidence interval; ER, estrogen receptor; OR, odds ratio; Q, quartile