Table 3. Adjusted odds ratios (OR) and 95% confidence intervals (CI) for the association between known and suspected risk factors and risk of molecular subtypes of breast cancer.
| Factor | Luminal A (n = 455) controls vs. | Luminal B (n = 72) vs. controls | HER-2/neu+ (n = 117) vs. controls | Triple negative (n =246) vs. controls | |||||||
|---|---|---|---|---|---|---|---|---|---|---|---|
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| OR | (95% CI) | OR | (95% CI) | pTHa | OR | (95% CI) | pTHa | OR | (95% CI) | pTHa | |
| Age at diagnosis | 1.08 | (1.06, 1.11) | 1.01 | (0.97, 1.06) | 0.0030 | 1.04 | (1.00, 1.08) | 0.07 | 0.99 | (0.97, 1.02) | <0.0001 |
| Age at menarche per 2 years | 0.87 | (0.75, 1.01) | 0.60 | (0.42, 0.85) | 0.13 | 0.82 | (0.63, 1.07) | 0.79 | 0.98 | (0.81, 1.18) | 0.12 |
| Nulliparous | 3.02 | (1.47, 6.23) | 4.11 | (0.80, 21.07) | 0.82 | 2.21 | (0.60, 8.16) | 0.68 | 1.08 | (0.41, 2.81) | 0.066 |
| Age at first birth per 5 years (among parous) | 1.16 | (1.01, 1.33) | 1.31 | (0.95, 1.80) | 0.64 | 1.19 | (0.93, 1.53) | 0.91 | 1.08 | (0.90, 1.31) | 0.48 |
| Months of breastfeeding per 6 months (among parous) | 0.94 | (0.86, 1.02) | 0.70 | (0.48, 1.01) | 0.15 | 0.85 | (0.70, 1.04) | 0.35 | 0.76 | (0.64, 0.90) | 0.039 |
| BMI per WHO categoryb (by menopausal status) | |||||||||||
| Premenopausal | 1.11 | (0.84, 1.48) | 1.73 | (1.07, 2.77) | 0.088 | 0.67 | (0.32, 1.41) | 0.22 | 1.67 | (1.22, 2.28) | 0.026 |
| Perimenopausal | 0.81 | (0.56, 1.17) | 1.27 | (0.63, 2.56) | 0.19 | 0.55 | (0.23, 1.33) | 0.46 | 0.92 | (0.56, 1.50) | 0.41 |
| Postmenopausal | 1.16 | (0.87, 1.54) | 0.83 | (0.36, 1.93) | 0.58 | 0.93 | (0.57, 1.52) | 0.53 | 1.02 | (0.70, 1.48) | 0.72 |
| Ever use of oral contraceptives | 0.81 | (0.64, 1.03) | 1.09 | (0.62, 1.94) | 0.64 | 1.10 | (0.71, 1.71) | 0.46 | 1.21 | (0.87, 1.67) | 0.26 |
| Benign breast disease | 1.89 | (1.43, 2.50) | 1.25 | (0.58, 2.67) | 0.41 | 0.86 | (0.45, 1.62) | 0.028 | 1.01 | (0.65, 1.58) | 0.018 |
| Positive family history of breast cancer | 1.93 | (1.38, 2.70) | 1.17 | (0.46, 2.97) | 0.28 | 0.95 | (0.43, 2.09) | 0.095 | 2.54 | (1.70, 3.82) | 0.32 |
Adjusted for all variables in table as well as study site and menopausal status
a
pTH p-values were calculated based on comparisons of each tumor subtypes compared to the luminal A group using a polytomous regression model adjusted for all variables in the table as well as study site and menopausal status
b
World Health Organization (WHO) categories of BMI were treated as an ordinal variable and included underweight (BMI< 18.5 kg/m2), normal weight (18.5 to <25.0 kg/m2), overweight (25.0−<30.0 kg/m2), and obese (30.0+ kg/m2)