Table 2.
Adjusteda odds ratio (OR) and 95% confidence interval (CI) for breast cancer overall and ER/PR/HER2-defined subtypes associated with BMI in premenopausal women and postmenopausal women
| Controls | All cases | Triple negative (ER–/PR–/HER2–) | Luminal-like (ER+ and/or PR+) | HER2-enriched (ER–/PR–/HER2+) | Unclassified | ||||||
|---|---|---|---|---|---|---|---|---|---|---|---|
| Number | Number | OR (95% CI) | Number | OR (95% CI) | Number | OR (95% CI) | Number | OR (95% CI) | Number | OR (95% CI) | |
| Premenopausal | |||||||||||
| BMI at age 18 years, kg/m2 | |||||||||||
| < 20.0 | 588 | 1187 | Referent | 160 | Referent | 656 | Referent | 71 | Referent | 300 | Referent |
| 20.0–24.9 | 543 | 1067 | 0.99 (0.84–1.16) | 144 | 0.91 (0.69–1.20) | 577 | 0.97 (0.81–1.17) | 55 | 0.82 (0.55–1.22) | 291 | 1.09 (0.88–1.35) |
| ≥ 25.0 | 126 | 173 | 0.72 (0.53–0.96) | 25 | 0.62 (0.36–1.04) | 83 | 0.63 (0.44–0.91) | 6 | 0.36 (0.14–0.92) | 59 | 1.00 (0.68–1.46) |
| Per 5 kg/m2 increase | 0.83 (0.73–0.95) | 0.68 (0.53–0.87) | 0.80 (0.68–0.95) | 0.59 (0.40–0.86) | 1.00 (0.84–1.19) | ||||||
| P value | 0.007 | 0.002 | 0.008 | 0.006 | 0.98 | ||||||
| P value for homogeneity of slope coefficients across three subtypes = 0.15 | |||||||||||
| Recent BMI, kg/m2 | |||||||||||
| < 25.0 | 758 | 1545 | Referent | 194 | Referent | 868 | Referent | 80 | Referent | 403 | Referent |
| 25.0–29.9 | 299 | 533 | 0.90 (0.74–1.08) | 80 | 1.07 (0.78–1.47) | 269 | 0.82 (0.65–1.02) | 29 | 0.99 (0.61–1.60) | 155 | 0.92 (0.71–1.17) |
| ≥ 30.0 | 200 | 349 | 0.85 (0.67–1.08) | 55 | 1.12 (0.75–1.67) | 179 | 0.80 (0.60–1.06) | 23 | 1.34 (0.75–2.38) | 92 | 0.75 (0.54–1.03) |
| Per 5 kg/m2 increase | 1.00 (0.92–1.08) | 1.14 (1.00–1.31) | 0.97 (0.88–1.07) | 1.19 (0.98–1.45) | 0.94 (0.84–1.05) | ||||||
| P value | 0.94 | 0.06 | 0.58 | 0.07 | 0.26 | ||||||
| P value for homogeneity of slope coefficients across three subtypes = 0.02 | |||||||||||
| Postmenopausalb | |||||||||||
| BMI at age 18 years, kg/m2 | |||||||||||
| < 20.0 | 522 | 734 | Referent | 89 | Referent | 358 | Referent | 40 | Referent | 247 | Referent |
| 20.0–24.9 | 518 | 673 | 0.92 (0.78–1.10) | 83 | 0.97 (0.69–1.39) | 326 | 0.94 (0.76–1.17) | 35 | 0.88 (0.53–1.44) | 229 | 0.89 (0.70–1.12) |
| ≥ 25.0 | 89 | 100 | 0.79 (0.56–1.11) | 14 | 1.01 (0.52–1.98) | 56 | 0.99 (0.65–1.50) | 5 | 0.76 (0.27–2.14) | 25 | 0.51 (0.31–0.85) |
| Per 5 kg/m2 increase | 0.98 (0.85–1.14) | 0.98 (0.73–1.32) | 1.12 (0.94–1.35) | 0.76 (0.48–1.20) | 0.86 (0.70–1.05) | ||||||
| P value | 0.81 | 0.89 | 0.21 | 0.23 | 0.14 | ||||||
| P value for homogeneity of slope coefficients across three subtypes = 0.20 | |||||||||||
| Recent BMI, kg/m2 | |||||||||||
| < 25.0 | 513 | 747 | Referent | 83 | Referent | 390 | Referent | 36 | Referent | 238 | Referent |
| 25.0–29.9 | 353 | 435 | 0.95 (0.78–1.16) | 64 | 1.11 (0.76–1.63) | 193 | 0.88 (0.69–1.12) | 28 | 1.23 (0.71–2.12) | 150 | 0.93 (0.71–1.21) |
| ≥ 30.0 | 263 | 325 | 1.09 (0.86–1.39) | 39 | 0.95 (0.59–1.55) | 157 | 1.19 (0.89–1.60) | 16 | 1.11 (0.55–2.25) | 113 | 1.03 (0.75–1.41) |
| Per 5 kg/m2 increase | 0.97 (0.90–1.06) | 0.97 (0.82–1.15) | 0.98 (0.89–1.09) | 1.06 (0.83–1.34) | 0.95 (0.85–1.07) | ||||||
| P value | 0.54 | 0.74 | 0.74 | 0.66 | 0.39 | ||||||
| P value for homogeneity of slope coefficients across three subtypes = 0.83 | |||||||||||
| Postmenopausal/never used MHT | |||||||||||
| Recent BMI, kg/m2 | |||||||||||
| < 25.0 | 186 | 283 | Referent | 33 | Referent | 148 | Referent | 15 | Referent | 87 | Referent |
| 25.0–29.9 | 150 | 181 | 0.94 (0.68–1.29) | 27 | 0.92 (0.50–1.71) | 74 | 0.82 (0.55–1.21) | 11 | 0.98 (0.41–2.34) | 69 | 1.06 (0.70–1.61) |
| ≥ 30.0 | 130 | 186 | 1.39 (0.98–1.99) | 20 | 0.96 (0.50–2.00) | 86 | 1.55 (1.00–2.41) | 9 | 1.20 (0.44–3.30) | 71 | 1.42 (0.90–2.25) |
| Per 5 kg/m2 increase | 1.07 (0.95–1.21) | 0.99 (0.77–1.27) | 1.07 (0.92–1.25) | 1.10 (0.77–1.56) | 1.10 (0.94–1.28) | ||||||
| P value | 0.27 | 0.94 | 0.36 | 0.60 | 0.26 | ||||||
| P value for homogeneity of slope coefficients across three subtypes = 0.81 | |||||||||||
| Postmenopausal/ever used MHT | |||||||||||
| Recent BMI, kg/m2 | |||||||||||
| < 25.0 | 327 | 464 | Referent | 50 | Referent | 242 | Referent | 21 | Referent | 151 | Referent |
| 25.0–29.9 | 203 | 254 | 0.93 (0.72–1.21) | 37 | 1.12 (0.67–1.87) | 119 | 0.89 (0.65–1.22) | 17 | 1.41 (0.68–2.90) | 81 | 0.86 (0.60–1.22) |
| ≥ 30.0 | 133 | 139 | 0.86 (0.62–1.20) | 19 | 0.87 (0.44–1.69) | 71 | 0.94 (0.63–1.42) | 7 | 0.91 (0.33–2.50) | 42 | 0.75 (0.47–1.19) |
| Per 5 kg/m2 increase | 0.90 (0.79–1.01) | 0.96 (0.75–1.21) | 0.92 (0.79–1.06) | 1.01 (0.71–1.42) | 0.82 (0.69–0.98) | ||||||
| P value | 0.07 | 0.71 | 0.24 | 0.98 | 0.03 | ||||||
| P value for homogeneity of slope coefficients across three subtypes = 0.85 | |||||||||||
Abbreviations: ER estrogen receptor, PR progesterone receptor, HER2 human epidermal growth factor receptor-2, BMI body mass index, MHT menopausal hormone therapy
aORs obtained from multivariable polychotomous unconditional logistic regression models with mutual adjustment of BMI at age 18 years and recent BMI and with adjustment for source study, study site, race, education, reference age, first-degree breast cancer family history, age at menarche, number of completed pregnancies, lifetime recreational physical activity, alcohol intake, cigarette smoking status, and oral contraceptive use
bModel described (a) is additionally adjusted for MHT use